Responsible for defending against the Turkish threat (1306), the Knights of St John based themselves in this fortified part of the city called the Collachium. A visit to the Paláti Megálon Magístron (Palace of the Grand Masters), built in the 14C in the northwest corner of the ramparts (Hellenistic and Roman mosaics from the Dodecanese Islands), is a must. Odós Ipotón, a medieval street lined with ''inns'' (15C-16C Gothic buildings in which the knights lived) is also worth a visit.