The church of San Liberato can be considered the only one of its kind. It is located within the botanic garden, between flowers and magnificent trees from all over the world. The church is dedicated to the martyrs Marco and Marciano and has an important historical and artistic value.
Nowadays, San Liberato has a colonnade with a bell tower on the south-east corner. Inside, the building has a single nave with apse and a presbytery, elevated above to level of the nave. Under the presbytery there is a circular crypt and a small apse chapel, which is on the right side of the altar and is used as a sacristy.
At the side of the building there are rooms which were used in the past as cells. Based on the analysis of the walls and the marble finds, the building is the result of alterations performed throughout the centuries.
We can distinguish at least five architectural interventions between XI and XVI centuries. During the first intervention, a rectangular room was built on some remains from the Roman times, which cannot be identified anymore. Seemingly, the room was built on a crypt without apse, which could be accessed through a door, supposedly under the present entrance.
Subsequently, during the X century, a small nave was added. This made it necessary to open two arches on the north perimeter wall and one in the area of the presbytery. During the third architectural stage an apse half-dome was added to the nave. An element that can help date the different phases is the pictorial decoration frescoed with velaria motifs, which is still visible on the base of the apse and merely identifiable on the soffit from the XII century.
Even though its precise dating is still uncertain, the tower bell cannot be dated after the XII century. Between XV and XVI centuries, the Augustinians commissioned a range of interventions on the building. Allegedly, the Augustinians also introduced the worship of Saint Liberato, Saint Augustin devotee.
A great help for the dating of the different parts of the building came from the investigation conducted between 1962 and 1963 by the British School in Rome and precisely by Dr. J. Gibson. The apse fresco is partly lost in the upper part, due to the enlargement of some windows (presumably during XV century, as well) which became rectangular and were then restored to their original arched shape in 1961. Besides that, the British School commissioned a general cleaning of the brick floor and the reinforcement of the ceiling beams.
As mentioned before, during the investigation different archaeological remains were found and Count Sanminiatelli used a chronological order to arrange them. The remains from the classical period were placed in the external colonnade, while the medieval ones, more relevant to the building, were located inside.