Kozani's cathedral, Ayios Nikolaos, is a three-aisled vaulted basilica with a pitched roof. Its cornerstone was laid in 1664 by the town's leading notable Harisis Trantas, and it underwent subsequent extensions and repairs in the 18th and early 20th century.
An inscription dates its wall-paintings, the work of the brothers Nikolaos and Theodoros from Ioannina, to 1770. Its carved wooden iconstasis, altar, pulpit, and bishop's throne -- all decorated with plants, animals and human figures -- are true works of art. The name of their creator, Bandoveris, as well as all the cost of the wooden furniture, are noted in a codex from the mid-17th century.
Another of the church's treasures is the embroidered 'epitaphios' (shroud) belonging to a certain Georgios Kontaris (1672). The seven storey bell tower, built in 1855, rises next to the church.