The Ruprecht Building is the oldest surviving residential palace within Heidelberg Palace. Its uninterrupted facade and Gothic entrance make it one of the few surviving remnants from the late medieval castle. The once single-story, simple structure was built under King Ruprecht I, who ruled between 1400 and 1410. His coat of arms, comprising an imperial eagle, a Palatine lion and the Wittelsbach rhombus, is depicted on the facade. It references his claim of royal dignity within the Holy Roman Empire.