 He spent months in the Catacomb of Callixtus, outside of Porta San Sebastiano, working under candle-light and drawing sepulchral inscriptions and murals of the first Christians.Many of these drawings made it into the publication on the illustrated book on the Catacombs by the Christian archeologist Giovanni Battista de Rossi.Mariani also made many lithographic designs for the Bulletin of the Roman Archeologic Commission.