A few minutes south of the centre, Kadzielnia is the strangest park in Kielce — a deep oval pit of pale limestone cliffs, ringed by trees and crossed by paths, with a startling view down into a green lake at the bottom. It is the remains of a quarry that operated until 1962. The cliffs are now a geological reserve, and at the eastern edge you can climb a steel viewing platform that hangs out over the void.
Beneath the hill runs a network of caves, opened to the public in 2011. Guided tours of about 50 minutes wind through several chambers with stalactites, fossil corals, and a small permanent exhibit on the geology of the Holy Cross Mountains. On summer evenings the amphitheatre cut into the eastern wall hosts concerts; check the schedule before you visit, since access is restricted on event days.