Micklegate Bar is one of the best preserved of York’s mediaeval gateways. The original 12th century gatehouse was replaced in the 14th century with a heavy portcullis and a fortified barbican, with upper floors containing living quarters, which today contain a museum describing the history of the gate and also the history of the City. It’s mildly diverting, but to be honest I’d stick to a walk around the walls, and clamber down for a better look at the gate itself. By tradition, it was the gate through which monarchs and other worthies entered the city, which led to it being used to display the decapitated heads of executed traitors