Roskilde is Zealand's second-largest town and one of its oldest, having been founded in 998. The town is named for a Viking king called Ro, who, according to legend, built the city around a lovely spring—"kilde" in Danish. In the Middle Ages Roskilde was one of northern Europe's largest and most important cities with a population of 5,000 to 10,000. Its eccentric, enormous cathedral, built in 1170, is a UNESCO World Heritage
Site. These days Roskilde is a university town known for hosting an enormous rock festival every summer. It makes a great base for exploring nearby historic areas like Lejre and Skibby.