The tower of the lions is now in ruins. These are the last vestiges of the barbican that protected the front of the castle before any enemy could reach the entrance. A barbican is a military building designed to maneuver the troops and allow the assailant to fire safely.
Tower of the lions
Nowadays we see the foundations and the pits near the moat. There were statues of wild animals, for there were lions of the menagerie, the latter belonging to the system of defense, with their roars which, it seems, chilled the blood. (learn more about the menagerie). In 1936 archaeological excavations were undertaken on this site and it was found bones of lions older than 600 years.
The map of the tower of London with the list of the buildings