Heidelberg Castle (German: Heidelberger Schloss) is a ruin in Germany and landmark of Heidelberg. The castle ruins are among the most important Renaissance structures north of the Alps.

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 1214 and later expanded into two 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 caused a fire which destroyed some rebuilt sections.

Early history

Heidelberg was first mentioned in 1196 as "Heidelberch". In 1155 Conrad of Hohenstaufen was made the Count Palatine by his half-brother Frederick Barbarossa, and the region became known as the Electorate of the Palatinate. The claim that Conrad's main residence was on the Schlossberg (Castle Hill), known as the Jettenbühl, cannot be substantiated. The name "Jettenbühl" comes from the soothsayer Jetta, who was said to have lived there. She is also associated with Wolfsbrunnen (Wolf's Spring) and the Heidenloch (Heathens' Well). The first mention of a castle in Heidelberg (Latin: "castrum in Heidelberg cum burgo ipsius castri") is in 1214, when Louis I, Duke of Bavaria of the House of Wittelsbach received it from Hohenstaufen Emperor Friedrich II. The last mention of a single castle is in 1294. In another document from 1303, two castles are mentioned for the first time:

• The upper castle on Kleiner Gaisberg Mountain, near today's Hotel Molkenkur (destroyed in 1537);
• The lower castle on the Jettenbühl (the present castle site).

All that is known about the founding of the lower castle is that it took place sometime between 1294 and 1303. The oldest documented references to Heidelberg Castle are found during the 1600s:

• The Thesaurus Pictuarum of the Palatinate church counsel Markus zum Lamb (1559 to 1606);
• The "Annales Academici Heidelbergenses" by the Heidelberg librarian and professor Pithopoeus (started in 1587);
• The "Originum Palatinarum Commentarius" by Marquard Freher (1599);
• The "Teutsche Reyssebuch" by Martin Zeiller (Strasbourg 1632, reprinted in 1674 as the "Itinerarium Germaniae").

All of these works are for the most part superficial and do not contain much information. In 1615, Merian's Topographia Palatinatus Rheni described Prince Elector Ludwig V as he "started building a new castle one hundred and more years ago". Most of the descriptions of the castle up until the 18th century are based on Merian's information. Under Ruprecht I, the court chapel was erected on the Jettenbühl.