Derry's city walls are the best-preserved town fortifications in Ireland or Britain, and one of the finest examples in Europe. Built between 1613 and 1619 by the London guilds as part of the Plantation of Ulster, the walls form a complete circuit of about 1.5 kilometres that you can walk in their entirety, free of charge, at any time.
The walkway sits on top of walls that vary between 4 and 10 metres in height and are broad enough to walk two abreast. The views from the top are excellent: down into the old city on one side, across the Bogside on the other, and to the River Foyle beyond. Four main gates — Bishop's Gate, Ferryquay Gate, Butcher's Gate, and Shipquay Gate — interrupt the circuit, and cannon remain in position on several of the bastions. The walls passed through the Troubles largely intact, despite their obvious symbolic significance.
The free-to-enter Tower Museum, inside the walls near Shipquay Gate, covers the history of the city from its monastic origins to the present day.