Bolu sits in the green, damp mountains between Istanbul and Ankara, a city that many people only see from the highway. That is a pity. The town itself is modest, but it makes a good base for some of western Turkey's most appealing lake and forest country.
The main draw is nature. Lake Abant National Park has a broad mountain lake ringed by forest and walking paths, while Yedigoller National Park is the wilder autumn classic, with seven small lakes tucked among beech, oak, and hornbeam. Closer to town, Golcuk Nature Park is the easy half-day choice, especially if you want a lake walk without a long drive.
Bolu also has a food reputation in Turkey. The nearby town of Mengen is famous for training chefs, and local menus lean into mountain cooking: soups, stuffed greens, rice dishes, cheese, and hearty bread. It is not a place for grand monuments, though Bolu Museum gives the city a useful historical anchor, with finds from the ancient Bithynian and Roman layers of the region.
Come for a spare day if you are crossing between Istanbul and Ankara and want forest air instead of another motorway stop. Stay longer if you want to use Bolu as a base for Abant, Yedigoller, and the wider Black Sea foothills.