The small, rather bland town of Duragan (133 kilometers south of Sinop) would be a place to just pass through if it wasn't for the Durak Hani. This Seljuk caravanserai was built in 1266 by Pervane Süleyman. It boasts a large summer courtyard surrounded by vaulted chambers leading to a triple-aisled winter hall.
The fortified complex has semi-circular towers on each corner, and the external walls are reinforced with additional rectangular towers. If you're interested in caravanserai architecture, it's well worth a stop on a Black Sea road trip