Eastern Marmara

• — one of the largest cities of the region, tried hard by the 1999 earthquake
• — resort town at the mouth of the Gulf of İzmit; its setting on a narrow strip of land between the sea and the verdant steep mountains is reminiscent of the Black Sea resorts in the Caucasus
• — it is a pity that the travellers taking the ferries across to Yalova from here don't take more time to look around this coastal village in the outskirts of Istanbul, topped by an ancient castle
• — Istanbul's overgrown industrial suburb has an interesting Ottoman mosque complex in its centre
• — home of the imperial carpet workshop and the waterside mansion built specifically for Kaiser Wilhelm's visit in 1884
• — Turkey's furniture capital boasts a well-curated city museum
• — at the end of the Gulf of İzmit, this large city is the heart of much of the Turkish heavy industry
• — historic town best known for its role in early Christianity, when it served as the site of the Councils of Nicaea
• — usually off the travellers' radar, this town nestled in the valley of the Sakarya River is full of white-washed Ottoman architecture
• — pleasant lakeside town east of Izmit, surrounded by lush forests
• — small town settled in the 13th century by yurt-dwelling Kayı tribe of the Oghuz Turks, out of whom the Ottoman Empire grew
• — well preserved old town inside the forests, with thermal springs
• — coastal city best noted for its hot springs dotting the forested mountains nearby, and its floriculture
• — agricultural town with a traditional bazaar area and an Ottoman mansion converted to a museum

• — skiing resort east of İzmit
• — hot springs near İnegöl

More or less corresponding to ancient Bithynia, the region is bordered by Istanbul Province to the northwest, the Western Black Sea Region to the east, Western/Central Anatolia to the south, and the Southern Marmara Region to the west.
There are a few things that are common throughout the region wherever you go:
The lush mountain scenery is everywhere, with the intervening valley bottoms providing much of the Turkish fruit and olive. Coupled with the uniformly well-maintained roads going up and down these ranges, driving through the region is a very pleasant experience.
You are never too far away from water: the sword-like Gulf of İzmit cuts deep through the region, and extensive beaches rim the long Black Sea coast in the north. The Lake Sapanca and the turquoise Lake İznik are among the largest in the country, and preferred by mid-class Turkish families favouring a milder climate and a "tamer" vacation compared to the Aegean and Mediterranean coasts, without all the hard partying going on in, say, Bodrum. Together with its beautiful gorge, the Sakarya River is a major feature in the east. Add the waterlily-filled floodplain forests near the river's mouth, hot springs and waterfalls here and there to the mix, and you will get the picture.
And the landscape is sprinkled by old town all around the region — some in a much better shape than others — except maybe the industrial suburbs along the northern coast of the Gulf of İzmit (but even there you will find that many towns have kept their historic cores intact). These towns lie at the very roots of the Ottoman Empire, which began in the late 13th century as a semi-nomadic petty kingdom in the area.

Welcoming fast ferries and "sea buses" (catamaran type passenger-only ferries) from various ports on both sides of the Bosphorus in Istanbul, Yalova is an easy entry point into the region, with direct connections to various towns.
The motorway O-4/E80, connecting Istanbul with Ankara, provides another easy connection into the region, as does the highway D-650 which connects with Eskişehir and Antalya in the south.
Major cities and towns in the region have bus connections with elsewhere in the country. Bursa is the hub for smaller towns in the southwest of the region thanks to the extensive minibus connections, while Eskişehir plays a similar role for those in the southeast.
There is an airport 10 or so km west of Yenişehir, mainly serving Bursa, which means that for regional towns you may need to backtrack from there if you need to use public transport.
The high-speed railway between Istanbul and Ankara crosses through the region, making stops in major towns along its route.

By bus/minibus

Frequent buses and minibuses connect the regional towns with each other. In case you cannot find a direct service to your destination, pick one that heads for somewhere in the middle (such as Yenişehir when travelling from İnegöl to İznik), from where you can quickly transfer to another minibus bound for where you are heading.

By car

All major roads throughout the region are well-maintained, but not without sharp hairpin turns at parts.

By train

A railway line coming in from Istanbul, lies west-east along the northern shore of the Gulf of İzmit and southern shore of Lake Sapanca and passes through İzmit and Adapazarı, where it turns southwards and continues along the bottom of impressive rocky and wooded Sakarya Valley towards Eskişehir. This is part of the Istanbul–Ankara railway line, so has the most frequent intervals of passenger trains on any route in the country, at least once every two hours 8:30AM-midnight, with the section of the line between Istanbul and Adapazarı having even more frequent departures—which start earlier as well, around 6:30AM.

By boat

Sea buses connect a number of towns along the southern rim of the gulf with İzmit. There is also a ferry line connecting Yalova (or rather the Topçular harbour 15 km east of the city) with Eskihisar on either side of the gulf, in direct competition with (and cheaper than) the Osmangazi Bridge, which spans over the gulf at a nearby site.

On foot/hoof

Commemorating Evliya Çelebi, a 17th-century Ottoman traveller, the Evliya Çelebi Way is a long distance hiking and equestrian trail heading inland from the village of Hersek, on the Gulf of İzmit east of Yalova, passing through İznik and a series of historic villages on the northeastern foothills of Mt. Uludağ before crossing over the Domaniç Mountains into Inner Western Anatolia, eventually reaching out to Kütahya, Afyon, Uşak, and Simav.

Historic towns

If you need to pick one out of the regional towns, İznik would provide the highest return on investment, thanks to its large and quite underrated Byzantine, Seljuk and Ottoman heritage, and the easiness of getting there. The town is almost completely enclosed by Byzantine-era walls, with the renovated Hagia Sophia Cathedral being its centrepiece. The rest of the town is liberally dotted by Seljuk and early Ottoman mosques and tombs, some of which are decorated by the colourful local tiles, a tradition dating back centuries ago.
South from İznik, Yenişehir has a historic bazaar entered by a gate spanning over a footpath of flagstones. Unlike its counterparts in Istanbul or Bursa, this is a not-at-all touristy place and is fully dedicated to traditional occupations. One end of the bazaar is marked by an Ottoman clocktower and a beautiful town council building, while at the other stands the Şeki House, an Ottoman mansion converted to a museum.
Further south is İnegöl, with a historic house converted to the City Museum, nicely recreating scenes from the streets and the artisanship of the centuries past.
The travellers seeking out the Ottoman heritage will want to head east from here, through the gorge of the Hamzabey/Ermeni Derbendi Pass, an ancient route connecting the Anatolian plateau with the ports on the Sea of Marmara, to Söğüt, the earliest Ottoman capital. In the late 13th century, after migrating west from their homeland in Turkmenistan, the Kayı tribe of the Oghuz Turks settled in a semi-nomadic fashion in Söğüt, and declared their independence during the rule of Osman I (r. 1299–1324), naming their state after their sovereign. Söğüt features the tomb of Ertuğrul, the father of Osman I and under the rule of whom the Kayıs arrived in Söğüt, as well as a small mosque built by him.
Nearby Bilecik also features a couple of early Ottoman buildings in a beautiful setting overlooking a ravine: the tomb of Sheikh Edebali, an influential Sufi taught during the early years of the Ottoman Empire, and a mosque built by Orhan (r. 1324–1362), the second Ottoman ruler and the son of Osman I. The rest of the old town, though, was badly damaged during the Greco-Turkish War of 1919–22, and has been abandoned since.
North from Bilecik, clinging on a hillside of the Sakarya River valley is Osmaneli, a mixed bag of an old town, consisting of perfectly renovated old buildings as well as those in a serious dereliction — sometimes next door to each other. The local hilltop is dominated by the ruins of a massive Greek Orthodox church, abandoned since the 1920s. Now that the new motorway alignment bypasses the town, it receives almost no visitors.
Further north, the river valley widens into one of the largest flatlands in the country. In the countryside just south of the modern city of Adapazarı is the Sangarius Bridge, an impressive marble bridge built by the Eastern Roman emperor Justinian I (r. 527–565), so that his army could cross the often treacherous waters of the Sakarya/Sangarius River easily during the campaigns against the troublesome neighbours to the east. Due to the changes of the river's course in the meantime, its span is now over a narrow creek.
Past the river to the southeast, the town of Taraklı tucked away in heavily forested hills has undergone a fine renovation in the first decade of the 2000s, and is now a pretty old town of white-washed traditional houses. Taraklı can be considered part of the country's "old town belt" in northwestern Turkey, which extends all the way to Safranbolu.
Westwards, İzmit, the biggest regional city, has a hillside old town of sorts, with steep cobbled streets lined by wooden houses. Near the coast below is an archaeological museum, which exhibits remains of a time when the city was one of the capitals of the Roman Empire, and was known as Nicomedia. Also nearby is a palace, which served the Ottoman sultans as a hunting lodge.
On the northern rim of the Gulf of İzmit, Hereke was a major carpet weaving centre, its imperial factory, now a museum, being the origin of the carpets bedecking Ottoman palaces. Nearby is the waterside mansion built just in time for the visit of German Kaiser Wilhelm to the factory in 1884.
Further west, Gebze is the unexpected site of a beautiful Ottoman mosque complex, complete with a repurposed poorhouse and school surrounding the mosque, all engulfed by modern development.
The waterfront of nearby Eskihisar is graced by the wooden mansion of Osman Hamdi Bey (1842–1910), the founder of Istanbul's Archaeological Museum and one of the earliest modern Turkish painters.
On the southern coast of the Gulf, Karamürsel, named after an early Ottoman admiral, is the site of the open-air marble tomb of its namesake, while Yalova to the west is rather known for its early Republican heritage as it was the favourite retreat of the founder of the Turkish Republic, Kemal Atatürk.

Nature

The narrow Ballıkayalar Valley, east of Gebze, is popular among enthusiasts of both rock climbing and hiking. The offers of the Harmankaya Canyon, cut by a stream deep into marble rock, and its immediate surroundings east of Bilecik go beyond and include some good canyoning as well. There are also established hiking routes in the Sakarya valley, especially around the Doğançay village south of Adapazarı, leading to some remote waterfalls on the mountains. While detailed descriptions of some of the routes can be gathered online, none of them are waymarked.
And then there is the (partially) waymarked Evliya Çelebi Way, mentioned above at "get around". A through hike along the EÇW end-to-end, attempted by few people as of yet, reportedly takes a little more than 20 days.
Hot springs come out of numerous locations in the region; the three most popular developed springs are at Yalova, Oylat, and Taraklı — in that order.
The only regional skiing resort is on the aptly named Mt. Kartepe (Turkish for "snow hill"), just east of İzmit.

In general, the Turks are great meat lovers and Eastern Marmara is no exception. Although the receipes rarely differ much, many towns in the region are known for their meatballs (köfte), with İnegöl having a certain degree of national fame for its favourite delicacy.
With the water embedded so much in the regional geography, fish is also easy to comeby. Fish sandwiches are often quick meals in the towns on the sea. Inland, freshwater fish is more popular — the trout farms of the village of Maşukiye on the Lake Sapanca, for example, attract a large number of daytrippers from the neighbouring cities.
İzmit is famous for its pişmaniye, a dessert made up of rounded strands of butter and sugar, and is likened to cotton candy. Along the highways around the city are series of small stores advertising their pişmaniye with large signs — the going rate can be as low as 10 TL for five packages, and they nicely double as cheap last-minute presents from the region to take friends back at home.
As this is one of the main fruit-producing regions of Turkey, if you happen to be wandering around the countryside in autumn, expect many temperate fruits to be in abundance — particularly apples, pears, quince and cornels in the south, and hazelnuts and kiwifruit in the north.

The region can be considered somewhat conservative by the Western Turkey standards, so, while grabbing a couple bottles of beer from the nearest store is never too hard, don't expect something of especial note in regards to local alcoholic beverages.

While well-maintained, steep gradients of up to 10% — often coupled with hairpin turns — are not uncommon on the regional highways, so drive safe.

• Istanbul — heading west along the Gulf of İzmit, Istanbul's eastern suburbs are just around the corner.
• Bursa — this is the first major city that the Ottomans took control of, so is non-surprisingly full of Ottoman heritage.
• Southern Marmara — further onwards from Bursa, the southern coast of the Sea of Marmara is lined by a series of historic towns and beach resorts.
• Western Karadeniz — in a way, this is the natural extension of Eastern Marmara, with better preserved old towns, lusher forests, steeper mountains dotted by an almost uncountable number of extremely scenic lakes.
• Central Anatolia — in the southeast where the mountains give away for the endless steppelands of the Anatolian plateau, Eskişehir is a pleasant riverside city, with a colourful old town. In the south, across the Domaniç Mountains, Kütahya is just as pleasant, with a more traditional atmosphere.
• Bursa Province