The best way to get a feel for Derry's layout and history is to walk the 1.5km circumference of the city's walls. Completed in 1619, Derry's city walls are 8m high and 9m thick, and are the only city walls in Ireland to survive almost intact. The four original gates (Shipquay, Ferryquay, Bishop's and Butcher's) were rebuilt in the 18th and 19th centuries, when three new gates (New, Magazine and Castle) were added.

　　The walls were built under the supervision of the Honourable The Irish Society, an organisation created in 1613 by King James and the London livery companies to fund and oversee the fortification of Derry and the plantation of the surrounding county with Protestant settlers. The society still exists today (though now its activities are mainly charitable) and it still owns Derry's city walls.

　　Derry's nickname, the Maiden City, derives from the fact that the walls have never been breached by an invader.