Guests could drive their carriages through the large entrance portal into the gateway. This is flanked in the front part by raised side corridors with domed Doric columns. The three-nave portico follows the model of a "vestibule à ailes" as found in the Palazzo Farnese in Rome. In the rear part is one of the most impressive staircases in Basel. The elegantly curved banister was made by the builder Johann Rudolf Burckhardt in 1778/79 by the leading art locksmith of his time, Jean-Baptiste Pertois (1733-1812) from Strasbourg. Guests were able to get out of the carriage on dry feet and reach the upper floor via the sandstone staircase.