Plan on giving your feet a workout in York, a historic walled city about two hours north of London by rail. The compact riverside locale is packed with attractions, including the biggest Gothic medieval cathedral north of the Alps, the Jorvik Viking Centre and the Yorkshire Museum, which brims over with sculpture, jewelry and fossils from the area. Visit Clifford's Tower, built by William the Conqueror in 1069, for the one-two punch of history and great city views.