The history of the city of Ahlat goes all the way back to Sekjukis. Ahlat is mainly famous for two things: the “kümbet”s (toumbs of a certain form) and the large Seljuki cemetery. The art of walking-stick making is also another thing Ahlat is famous for.
There are currently 14 kümbets in the city, most of which are close to each other. The most famous one is right next to te Seljuki cemetery, so you can visit both of them at once conveniently.
But there are plenty of other things you can do in Ahlat. Seeing the ancient city of cave houses; visiting other kümbets, which all differ notably in style; visiting the old castle and the two old mosques that are located in it, seeing one of the two remaining walking-stick shops etc.
Local population is known to be very warm and hospitable. They might not even ask for money for their services if they see you are a foreigner. They don’t speak English though.