This so-called Public Building is in the north-west part of the Sacred Area of the Republican Temples, to the north of the Temple of Hercules. It has been dated to the period of Trajan (opus mixtum). The function of most of the rooms is unknown. In one of the central rooms a waterwheel was installed, that lifted ground water for use in the Baths of Buticosus to the east.
In the north-eastern room (directly to the west of the Tetrastyle Temple) wall-paintings have been preserved with red, green and yellow on a white background, especially on the east wall. They are probably Severan. Depicted are architectural motifs, fishes with tridents, festoons and other objects. The paintings seem to be have been divided by two semi-columns, resting on a marble base. In the east part of the north wall is a wall niche with a base or altar in front. In front of the north wall is a low bench (h. 0.30 - 0.45).