The castle has only been partially rebuilt since its demolition in the 17th and 18th centuries. It is located 80 metres (260 ft) up the northern part of the Königstuhl hillside, and thereby dominates the view of the old downtown. It is served by an intermediate station on the Heidelberger Bergbahn funicular railway that runs from Heidelberg's Kornmarkt to the summit of the Königstuhl.
The earliest castle structure was built before AD 1214 and later expanded into 2 castles circa 1294; however, in 1537, a lightning-bolt destroyed the upper castle. The present structures had been expanded by 1650, before damage by later wars and fires. In 1764, another lightning-bolt destroyed some rebuilt sections.When Rupert III of Germany became the King (Emperor) of Germany in 1401, the castle was so small that on his return from his coronation, he had to camp out in the Augustinians' monastery, on the site of today's University Square. What he desired was more space for his entourage and court and to impress his guests, but also additional defences to turn the castle into a fortress.After Ruprecht's death in 1410, his land was divided between his four sons. The Palatinate, the heart of his territories, was given to the eldest son, Ludwig III. Ludwig was the representative of the emperor and the supreme judge, and it was in this capacity that he, after the Council of Constance in 1415 and at the behest of Emperor Sigismund, held the deposed Antipope John XXIII in custody before he was taken to Burg Eichelsheim (today Mannheim-Lindenhof).