Tradition has it that Saint Cleto was the first bishop of the city and that this place was used by the first persecuted Christians. In reality, these are structures from the Roman era used to collect water to supply the city or a Roman spa nearby.
P. Testini, Le prime memorie cristiane e la cripta detta di S. Cleto a Ruvo, in Vetera Christianorum, I, 1967, pp. 185-210. N. Lavermicocca, La Grotta di S. Cleto a Ruvo di Puglia, Ruvo di Puglia, 1990. V. A. Sirago, Puglia Romana, Bari, 1993, p. 27 http://www.confraternitapurgatorio.it/la-chiesa/ipogeo-e-grotta-di-san-cleto/?doing_wp_cron=1583928447.8000309467315673828125