The Fourth Courtyard is the smallest and at the same time the oldest courtyard of the castle. The original castle core with medieval foundations was built around it. The courtyard is dominated by a well that is 26 metres deep and reaches into the castle cave. It was dug in the place of the original narrow channel through which the water came to the surface. During its excavation, a spacious cave was discovered in the body of the travertine mound.

The rods with the decorative heads on the façade of the Middle Castle reinforce the old perimeter walls, which have undergone many structural modifications over the centuries. Like other decorative metal elements in the castle, the rod heads, as well as the handles for the lightning conductor, the iron lamps and the decorative grille on the well were made by the Bratislava firm of Louis Márton and son, artistic blacksmithery, at the turn of the 19^th and 20^th centuries.