Osmaneli's old town is the real reason to walk around rather than just photograph a church and leave. The best streets are in Camii Kebir and Camii Cedid, where whitewashed, timber-framed houses still show the form of an old Sakarya valley town.
Much was lost in the 1874 fire, and not everything that survives is restored. That unevenness matters. Osmaneli feels lived-in and a little forgotten, which makes the old houses more interesting than they would be as a scrubbed heritage quarter.