Beneath the Market Square is a chain of medieval cellars carved into the bedrock — at its lowest point, 25 metres underground, the deepest cellar system open to visitors in Poland. The tour is guided (in Polish, with English audio guides) and takes about 45 minutes, threading through 34 chambers connected by stone-cut passages.
The exhibits along the route cover Rzeszów's history from its founding in 1354 — merchant trade, the Lubomirski family, the Jewish community, the Galician partition — using artefacts found during the excavations and reconstructions of period rooms. The cellars themselves are the real attraction: vaulted, candle-cool, and quietly atmospheric. Bring a jacket; it is ten degrees down there year-round.