The ground around Roskilde was once walked by Viking warriors. Travel to the Viking Ship Museum in this ancient town to see the thousand-year-old remains of five Viking longboats excavated from the bottom of Roskilde Fjord. Outside, you'll find Museum Island, an archaeology workshop and, during the summer, a working Viking boatyard where master craftsmen make replicas of Viking-age wooden boats and longboats, using the same materials and techniques as their Viking ancestors. Step inside Roskilde Cathedral – a UNESCO World Heritage Site and Scandinavia's earliest brick Gothic cathedral. With its tall spires, this magnificent church is one of Denmark's most important architectural monuments. Today's cathedral dates only from the 12th century, but many of its architectural details, such as porches and side chapels, were added in subsequent centuries. Danish monarchs are buried in Roskilde Cathedral, all in very ornate tombs. Harald Bluetooth – perhaps Denmark's most famous king – is buried here, too. Keep an eye out for the richly decorated bronze statues, huge frescoes and paintings, and wooden choir stalls carved with reliefs and scenes from Creation to the Last Judgment – these are all testament to the importance of the cathedral.