Lying east of the Sea of Marmara in Turkey, Eastern Marmara (Turkish: Doğu Marmara) has everything in it from expansive industrial wastelands interrupted by endless suburbia of high rises to untouched mountainous wilderness dotted by well-preserved cute Ottoman old towns.
- Adapazarı — one of the largest cities of the region, tried hard by the 1999 earthquake
- Eskihisar — 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
- Izmit — at the end of the Gulf of İzmit, this large city is the heart of much of the Turkish heavy industry
- Iznik — historic town best known for its role in early Christianity, when it served as the site of the Councils of Nicaea
- Osmaneli — usually off the travellers' radar, the historic core of this town nestled in the valley of the Sakarya River, just off the highway south, is full of white-washed Ottoman architecture
- Sapanca — pleasant lakeside town east of Izmit, surrounded by lush forests
- Söğüt — small town settled in the 13th century by yurt-dwelling Kayı tribe of the Oghuz Turks, out of whom the Ottoman Empire grew
- Taraklı — well preserved old town inside the forests, with thermal springs
- Yalova — coastal city best noted for its hot springs dotting the lush mountains nearby, and its floriculture
Eastern Marmara is bordered by Istanbul Province, Southern Marmara, Central Anatolia, and Western Black Sea Region to northwest, southwest, south/southeast, and east respectively. To the north, it occupies part of Turkish Black Sea coast, while to the west, the Gulf of İzmit, part of the Sea of Marmara, makes a long indentation into the region.
Eastern Marmara more or less corresponds to Bithynia of ancient times.
Being the cradle of Ottoman Emirate, later to become Ottoman Empire, this region is dotted by historical towns and villages maintaining traditional Ottoman architecture, if a bit weary. North of the region is the Black Sea coast with some resort villages largely missed by travellers, while on the coasts of Lake Sapanca and Lake İznik, two of the biggest lakes of the vicinity, are a number of summer resorts and beaches mostly frequented by Turkish mid-class families who prefer a milder (and tamer) alternative to Aegean and Mediterranean coasts.
Most of the region is mountainous, or at least hilly, and covered with verdant forests.
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.