Dating back from the Viking Age, Roskilde is an important stop between Copenhagen and the western regions of Denmark. The city prides itself with one of the most impressive cathedrals in Denmark. Built in the 12th and 13th centuries, the Roskilde Gothic Cathedral was the only cathedral in Zealand until the 20th century, attesting the city's early importance.The cathedral is the burial site for Danish monarchs and since 1995, it has been listed as a UNESCO World Heritage Site. Connected to the church is Roskilde Palace, built during 1733-36. Another attraction in the city is the Viking Ship Museum (Vikingeskibsmuseet). The centrepieces of its collection are the well-preserved remains of five Viking ships, excavated from nearby Roskilde Fjord in the late 1960s. The museum also undertakes research in experimental archaeology centred on Viking shipbuilding and seaworthiness.