In the 1930s, Saarbrücken's Schlossplatz was to be redesigned. The occasion was the visit of Adolf Hitler for the inauguration of the new gau theatre on 9 October 1938. The forecourt of the castle, with the Bismarck Monument and the Lancers' Monument, was to make way for a stairway with a balustrade in the style of an open-air theatre. However, during the excavations, the workers came across some remnants of walls and arches. It was a sensation! Without any doubt, other small finds and architectural remains were able to be classed as belonging to the development of the Schlossfelsen in mediaeval to early modern times. Until then, their existence had been a matter for mere conjecture. So the reconstruction was halted and the excavations extended.

They revealed a great deal: the foundations of the mediaeval keep and those of the two small baroque guard houses, the substructure of a drawbridge, the extensive defence installations of the castle from the 16th century with bastion and casemates, and a newel from the so-called summerhouse of 1577, which had been one of the count's other residences.