Kuenringerburg, the castle high on the hill above the town, is where Richard the Lionheart was incarcerated from 1192 to 1193. His crime was insulting Leopold V; his misfortune was to be recognised despite his disguise when journeying through Austria on his way home from the Holy Lands. His liberty was granted only upon payment of an enormous ransom of 35,000kg of silver (this sum partly funded the building of Wiener Neustadt).
An easy, yellow path starts at the Kremser Gate (marked 'Burgruine'); a more difficult route begins in the Altstadt (old town). It takes about 25 minutes to walk up to the ruins whichever path you follow. The ruins are great for scrambling around and there's an open-air exhibition of sorts providing background on the castle's history and the personalities associated with it.