Malta has examples of Neolithic and Bronze Age structures that are on the World Heritage List. These include the Hal Saflien Hypogeum, an enormous underground burial chamber, dating back to around 3600 B.C. and the seven Megalithic Temples of Malta on the islands of Malta and Gozo. Mdina and Rabat date back to the Bronze Age. Built on one of Malta's highest points, Medina has a number of medieval buildings: palaces, houses and a baroque cathedral.The historic city of Valetta, Malta's capital, is listed as a UNESCO World Heritage site. It has over three hundred historical monuments including the Palace of the Grand Masters, the Cathedral of St John and beautiful churches built by the Knights of Malta (the Order of St John). Two leading Maltese architects were Gerolamo Cassar (sixteenth century) and Tumas Dingli (early seventeenth century).