Kadaň was founded in the 13th century by King Přemysl Otakar II.
The Middle Ages gave rise to the town's most most significant sights, such as the Gothic castle with a part of its Gothic fortifications and a sizeable bastion in front of the Žatecká gate. The Gothic Town Hall dates back to the 14th-15th centuries; an attached high tower is topped by a rare stone helmet.
The square is decorated by Baroque facades of the older buildings and a Baroque plague column. A unique Late Gothic Franciscan monastery complex is located at the foot of Mount Strážiště; the monastery church houses a significant cycle of wall paintings, probably from the circle of Lucas Cranach the Elder.