There have been regular demonstrations on the part of Ungdomshuset supporters for the past six months, including violent riots in which police have basically given up control of the streets. In order to escalate the political side of the struggle, activists came up with a simple plan: go squat something big as a replacement for Ungdomshuset, do it in public, and make a bid for renewed public support by doing it in a confrontational but non-violent way. In a brazen display of self-confidence, the organizers released their planned starting point, as well as a full run-down of their planned tactics and the location of the building they plan to squat (an old waterworks).

The History of Ungdomshuset

Before its destruction on 5 March 2007, Ungdomshuset occupied social centre served as a central rallying point for the city's anarchist youth. The building, located at Jagtvej 69, Nørrebro hosted gigs and meetings for nearly 25 years. Its roots as a focal point for the city's left went back over a century.

From Wikipedia:

The building was completed on 12 November 1897, with the name "Folkets Hus" (The People's House). The house functioned as one of the resorts for the then-incipient labour movement of Copenhagen. Since labour organisations were unpopular in the eyes of the authorities, and reprisals were often carried out against them, the organisations had to build their own headquarters — Folkets Hus was the fourth of these to be built. The roots of several demonstrations and meetings were planted in Folkets Hus, and as a result it was strongly linked to the great demonstration against unemployment in 1918 when workers stormed the Danish Stock Exchange (Børsen). In 1910, The Second International held an International Women's conference at the house, during which Clara Zetkin launched the idea of an International Women's Day. Lenin and Rosa Luxemburg visited the centre.

For more background see the Ungdomshuset Wikipedia page.