Mikó Castle in the centre is the architectural anchor — a 17th-century Renaissance fortress now housing the Székely Museum of Csík. The Șumuleu Ciuc Shrine on the northern edge of town is the other obligatory stop and one of Central Europe's most important Catholic pilgrimage sites, especially around Whitsun.
Beyond those two, the town itself is pleasant rather than packed with sights — the main square, the Csíki Sör brewery tour, and a drive up to the Harghita Băi mountain resort for hiking or skiing fill out a full day. The surrounding forested mountains are the real draw if you have a car — the Csík Basin and the Hășmaș range are quiet and full of marked trails.