The pictorial decoration of the dome, in the foyer of the first floor was commissioned to Manuel Humbert (Spanish), Josep de Togores (Spanish)and Francesc Galí (Spanish). The first two painted the pendentives and the drum, while the latter was dedicated to the cupola of the dome, which brought together Religion, Science, the Fine Arts and the Earth. On the drum, Humbert and Togores represented eight generations: the Phoenicians, the Greeks, the Iberians, the Celts, the Carthaginians, the Romans, the Visigoths, and the Muslims. On the pendentives, in grisaille, allegories of Leon, Castile, Navarre and the Crown of Aragon are represented.  

Under the pictorial decoration, Enric Casanovas (Spanish)and Josep Dunyach (Spanish) sculpted, respectively, the personifications of Work and Religion, and of Law and Order in artificial stone.

On the floor a mosaic was paved, the central panel of which was the coat of arms of Barcelona, that occupied an area of 133 m² – currently in the storerooms of the museum, which had to be taken up due to the remodeling works that began in 1990. The rest of the pictorial and sculpted decoration is conserved just as it was in 1929. The Dome Room is a good venue for small events.