York has been the capital of the north of England for most of two thousand years. The Romans founded it as Eboracum in AD 71, and Constantine the Great was proclaimed emperor here in 306. The Vikings took it in 866 and called it Jorvik, and their word for street, gata, is why so many streets here end in "gate". In the Middle Ages it was England's second city, and it built a cathedral to match, York Minster, still one of the biggest Gothic churches in northern Europe. Then the railways came, and chocolate.
All of it is packed inside about two miles of medieval walls, the longest in England. York is small, about 200,000 people, and walkable, and its old streets are so crowded with timber-framed houses, churches and pubs that you'll keep finding new corners for days. Five days give you the city at a gentle pace, a Sunday roast and a day out to Whitby on the coast.
This plan starts on a Thursday. Day one is the Minster, the walls and the Shambles, day two the Vikings and the castle, day three Whitby on the coast, day four, a Sunday, Roman York, a roast and the railway museum, and day five chocolate, a Georgian house and the river. Whitby's abbey closes early in the week in winter, which is why the trip falls on a Saturday. For the bigger picture, see our page on the United Kingdom.