This museum is the Danish national museum for ships, seafaring and boatbuilding in the prehistoric and medieval period, and it houses the Skuldelev ships. They were deliberately sunk in the year 1070 to protect Roskilde from an enemy attack, and were later excavated in 1962. The museum was built especially for these ships plus 9 more discovered later, including the longest war ship ever discovered, at 36m long. Price of admission – 115DKK (15EUR or $17). Cheaper after Oct 18th.