The two fountains are placed symmetrically at the foot of the Capitol Hill Graded Ramp and present two basalt Egyptian lions, from whose mouth the water flows into two small ponds.
The lions come from the Iseum Campense (the temple built by Emperor Domitian in Campus Martius in honour of the Egyptian gods Isis and Serapis). They were then moved next to the entrance of the Church of Santo Stefano del Cacco.
In 1562 Pious IV Medici (1559-1565) donated them to the Roman people to decorate the graded ramp of the Capitol Hill and put on the bases designed by Giacomo Della Porta.
When the Acqua Felice was brought to the Capitol Hill, the lions were turned into fountains, putting two travertine chalices in front of them. In 1885 the small ponds were destroyed and the lions were moved to the Capitoline Museum and replaced with dull-grey marble copies. In 1956 they were put back into place and the small ponds were rebuilt according to old documents.