After climbing up the long road to the palace, upon entry one of the first buildings one comes upon (and which is in the best shape of almost any of the Heidelberg Castle buildings) is the Friederichsbau, built by Prince Elector Friederich IV. According to this webpage:

You will find the the castle's second Renaissance Palace between the Ladies Building and the Hall-of-Mirrors Building. The Palace owes its existence to Elector Friedrich IV. (1583-1610) and his master builder Johannes Schoch. The construction work started in 1601, first a chapel (1364) was completely disassembled and afterwards re-integrated into the ground floor. In 1604, the construction was finished, yet the sculptor Sebastian Görtz was working on the statues until 1607. These present the most important ancestors of Friedrich IV.

In contrast to Ottheinrich's Palace, the rear of the building is also decorated. Along with the castle, it was destroyed during the French Succession Wars in 1693. In 1900, the Palace was renovated and is therefore the only building in the castle that shows itself in such erstwhile magnificience.

Friederich IV Palace