In 1934, Heinrich Himmler decided that the castle (located not far from what was then believed to be the site of the Battle of the Teutoburg Forest) would be the ritual headquarters of the SS.
Summary of German site:
The Wewelsburg was built from 1603 to 1609 by the Prince of Paderborn. It lies in the quarter of the same name of the city Büren in the Paderborn district. Heinrich Himmler leased the castle 1934 for 100 years from the Paderborn district and wanted it at first to re-design it as the school for Nazi leadership (the so-called SS "Fuehrerkorps"). The plans of Himmler included making it the centre of a new Germanocentric world following the "final victory". As such an installation of a diameter of a kilometer designed in accordance with secular Nazi principles was planned, including a representational figure for the "Fuehrerkorps". When the final victory failed to materialize, Himmler in 1945 ordered the dynamiting of the Wewelsburg - but the arrival of American troops aborted the total destruction of the building, only the North Tower suffering great damage, and this was later restored.