Pope Pius IX chose to participate in the Universal Exhibition in Paris in 1867 in a grandiose manner, celebrating the architectural works and new institutions for Christian archaeology that he had promoted. The main attraction of the Papal State at the Universal Exhibition in Paris was located among the ephemeral structures in the park of the Champ de Mars. It was a small facsimile catacomb that ideally represented a prototype of a Christian cemetery with all its distinctive features. It was indeed a model of a catacomb in real size and volume, re-proposing open and closed galleries, a cubicle and the main Christian burial methods, and offering the visitor the experience of an inviolate Christian hypogeum.  The choice was to reproduce pieces -as well as their arrangement- that could explain clearly the oldest Roman catacombs and their main features.

It was a structure of wooden planks and cork, with an internal skeleton, covered by clods of earth and vegetation to create a mound It gave the impression of entering an underground environment like in the original ones. The front of the facsimile catacomb occupied almost nine metres and was decorated with casts of Christian inscriptions embedded between the entrance and exit doors. Visitors entered on the left and exited on the right.

From the entrance vestibule A one proceeded to gallery B, which showed all the features of the sepulchral tunnels, and then into gallery C, which had loculi on both sides, with copies of catacomb inscriptions and paintings such as the so-called Virgin of Priscilla. In the centre of the monument was chamber D, which aimed to represent a syntesis of all the cubiculae of the Roman catacombs in small scale, with reproductions of frescoes (in particular from St. Callistus) and a copy of the large central skylight from St. Callistus in the centre.