As we strolled the pedestrian-friendly streets of central Brno, I was struck both by its beauty and its lack of tourists. The Czech Republic’s second-largest city is a first-class pleasure to visit, with superb restaurants, convivial and stylish bars and a short list of fascinating sights, most famously the Villa Tugendhat, a functionalist masterpiece of residential architecture by Mies van der Rohe.

But many of Brno’s most interesting attractions are underground. The Czechs seem to have an affinity for the macabre, and Brno is no exception. We spent much of our time beneath the city exploring its underworld, where we discovered mummies, prison cells, an extensive labyrinth and vast piles of bones.

These are the city’s four most important underground attractions: