The Imperial Palace was the residence of the Habsburg emperor until 1918. From the 13th century until just before the end of the monarchy, the area was fitted out in imperial splendor with its present-day size. The original gothic building around today’s Schweizerhof was extended on a continuous basis, resulting in an extensive building complex formed of different sections, which contributes an essential character to the appearance of Vienna's Old City. Europe’s largest imperial cultural complex today houses more than two dozen collections of international standing, including the Austrian National Library, the Imperial Treasury, the Imperial Apartments and the Sisi Museum, as well as the Spanish Riding School.