The old city of Jerusalem has been populated for well over three thousand years. During that time it has been ruled by many different people. As the map shows, there are now four quarters: Muslim, Christian, Jewish and Armenian.
The walls of the old city, built in 1538 by Suleiman the Magnificent, contain eleven gates, seven of which are currently open. At the risk of sounding like a tourist guide, I recommend the rampart walk, which provides great views of the old city, as well as areas further afield.
Edit: The map has a mistake that’s very common here. People find it hard to believe that if there’s more than one lion you still say, “Lion Gate.” English!