A short distance to the south of the Alter Market square in central Cologne is the foundations of the Praetorium, or Governors Palace, from Roman times. This was one of the largest buildings in Roman Cologne. Also here are the remains of the Roman Canal sewer system, with vaulted ceilings and stretching 100 metres. Both of these are open to the public on certain days of the week, and for a small admission charge. Information on their history and excavations are presented.