The Byzantine Museum of Kastoria is the logical starting point for anyone who wants to understand the city's 1,000-year tradition of religious art. The collection holds over 700 icons, frescoes, sculptures, and liturgical objects drawn primarily from the city's own churches, and it is one of the better Byzantine collections in northern Greece.
The displays are well organised and the labelling is in both Greek and English. Highlights include a series of 12th and 13th-century icons with the intense gold backgrounds characteristic of the period, several large wall paintings removed from churches undergoing restoration, and a good selection of embroidered vestments and carved wood screens. If you are planning to visit the Byzantine churches on the peninsula (which you should), spend an hour here first — it makes the context much clearer.
The museum is open Tuesday to Sunday; closed Monday. It is located in a modern building near the main square, easy to find.