Sønderborg (German: Sonderburg), is a municipality (Danish, kommune) in Region Syddanmark partially on the Jutland peninsula and partially on the island of Als in south Denmark, at the border with Germany. The municipality covers an area of 499 km² (193 sq. miles), and has a total population of 76,825 (2007). Its mayor is Jan Prokopek Jensen, a member of the Socialdemokraterne political party. The site of its municipal council is the town of Sønderborg, which covers most of the area of the municipality. The municipality is split into two sections separated by Als Fjord, the waterway which separates the island of Als from the Jutland mainland. The town of Sønderborg lies on both sides of Als Fjord; the narrow strait between these two sides is called Als Strait (Alssund). Two road bridges connect the city across the strait: the 682-meter Als Strait Bridge (Alssundbro), built in 1978-1981; and the 331-meter King Christian X's Bridge (Kong Christian Xs Bro), built in 1925-1930.