The Manica Lunga cryptoporticus (Nomination file, p. 38)

There are many underground corridors such as underneath the Imperial Baths and the Forum. The word cryptoporticus is more explicitly used in connection to information about the Aula Palatina: Originally, the basilica was part of a larger palace complex. Several remains have been identified: a cryptoporticus near the entrance (to the south of the basilica), and parts of ancient mansions - from the first to the fourth century - in the northwest, with some nice black-and-white mosaics. See, e.g. On Imperial Traces.

The Roman Cryptoporticus, with entrance on the Piazza Duomo can be visited.

The English Garden has a cryptoporticus.

Domus Aurea and Palatinum

Abbey Saint-Jean de Sorde: cryptoporticus under the south terrace of the convent (Nomination file)

Pompei: House of the Cryptoporticus; Herculaneum: House of the Deers and House of the Mosaic Atrium

Monte Sant'Angelo: "At a later date, the rock partition dividing the two caverns was demolished, thus creating a single large space which was reached by means of a new monumental flight of steps (...). At the same time, the monumental flight of steps was linked by two spans, at the central body by a structure comprising five spans; an eighth span on the opposite side of the steps served as an entranceway into the structure which took the form of a 40-metre long arcade, a sort of cryptoporticus which also served the purpose of offering temporary shelter to pilgrims (hospitium)." (Nomination file, p. 215)

"From the crypt of the original cathedral of Santa Maria Maggiore you descend to an underground environment that corresponds to a Roman house dating back to the first century. AD. Excavations made in the nineteenth century and in the 50s of the twentieth century have unearthed three adjoining rooms and a cryptoporticus, with floors covered with mosaics (...)."
See www.visit-assisi.it