The unfortified "Untere Stadt" was devastated by Ottoman forces in the 1529 Siege of Vienna and the 1683 Battle of Vienna whereas the fortified "Obere Stadt" was successfully defended in both cases. In the 18th century Emperor Charles VI, who could not prevail in the War of the Spanish Succession, set up plans to rebuild the Klosterneuburg monastery complex modelled on the Escorial. The construction of the Baroque buildings began in 1730; however, it did not survive an initial phase.