Second appointment with the two-episode journey of "Ulisse: il piacere della scoperta" with Alberto Angela among the secrets of underground Rome. A city that never ceases to amaze us, which reveals new aspects among more recent neighborhoods with new buildings, the accumulation of debris, the raising of the walking surface which have made buildings which once constituted authentic wonders disappear underground and which sometimes they randomly re-emerge in all their splendor. This is the case of the Basilica of Porta Maggiore, discovered by chance during work on the railway viaduct leading to Termini Station. Or the hypogeum with magnificent frescoes, where Christian and pagan symbols mix, hidden under a manhole in the Appio Latino neighborhood. Or, again, of the astonishing maze of tunnels and service areas that hides underground of the grandiose Baths of Caracalla, and the small lake with pure water that was formed under ancient ruins on the Celian Hill.