The Notitia ecclesiarum urbis Romae refers to their being buried near the Catacomb of San Pancrazio - indeed, after a visit to that catacomb, the Notitias author made a pilgrimage to that now named after Processus and Martinianus without interrupting or deviating from his route, meaning they were very close to each other.
Other more recent scholars place the catacomb topographically closer to St Peter's Basilica, in the Janiculum area, where several underground burial chambers were found from the late 19th century onwards, particularly in the area around the Church of Sant'Onofrio al Gianicolo.
[1] In 1898, during the construction of a monastery of Sister Dorothea on the salita di Sant'Onofrio, a gallery with clear indications of Christian iconography were discovered.
Il Marucchi, who studied these galleries before their destruction, theorised that they were an extensive Christian cemetery which branched off towards the Vatican Basilica.
In 1980 Margherita Cecchelli theorised that these galleries formed part of the lost catacomb of Saints Processus and Martinianus, which extended from its most important nucleus under the Collegio Urbaniano.