Central Bohemia's biggest attraction is its Gothic castle Karlštejn, founded by Charles IV to store royal treasures including the Crown jewels and holy relics. About 30km (40 minutes by train) from Prague, it makes for an ideal day-trip from the capital, with coin-minting displays and a wax museum with effigies of Charles and his four wives. There are pleasant hikes in the surrounding national park, one them (fairly challenging) to a lovely monastery in the nearby village of Svatý Jan Pod Skalou, where you can also visit the holy hermit's cave it was built over.
Another highlight of the region are the old silver mines in the historic town of Kutná Hora, once part of the Cistercian monastery here. Kutná Hora (about 85km from Prague) and neighbouring Sedlec are a UNESCO World Heritage Site, with significant buildings including the Gothic St Barbara's Church, the Italian Court (once a royal residence and mint) and Sedlec's famous ossuary or 'church of bones', which includes a vast chandelier made from skulls and other human remains.