This is the Ulu Cami (Great Mosque). When exactly it was established is not known. It was fully rebuilt in 1678.
The austere outside aspect hides a nice and interesting interior, with good 17th century woodcarving and restored wall paintings called ‘kalem işi’ (= work of the pen/paintbrush).

Correspondent: J.M.Criel, Antwerpen.
Source: Website of ‘hsnymn.blogcu.com/tokat-merkez’