When St. Jerome was young (he says he was a “puer,” a boy, and he was about twelve) and was sent to study in Rome, he used to go along with his Christian friends on Sunday afternoon trips to the catacombs, to visit and pray at the tombs of the apostles or the other martyrs (or just to test their courage and explore places, because they were boys). And we know this because he talks about it in his Commentary on Ezekiel (40, 5-13).
“Often we would enter those crypts which have been hollowed out of the depths of the earth, and which, along the walls on either side of the passages, contain the bodies of buried people. Everything was so dark that the Prophet’s saying, ‘Let them go down alive to the underworld’ (Ps. 55: 15) seemed almost to have been fulfilled.
“Here and there a ray of light, admitted from above, relieved the horror of blackness, yet in such a way that you imagined that it was not so much a window as a funnel pierced by the light itself as it descended.
“Then we would walk back with feet feeling our way, wrapped in ‘unseeing night’ (Seneca the Younger, Thyestes, 668: “nocte caeca”), with Virgil’s line recurring to us: ‘Everywhere the terror” in our hearts, “and silence itself at the same time” terrified us. (Aeneid, Bk. 2, 1, 755: “Terror ubique animos, simul ipsa silentia terrent.”)”
So… yeah, St. Jerome apparently did this a lot, even though it scared the dickens out of him and the other kids. Not exactly an advertisement for taking the Scavi tours in Rome, I gotta say!
I wish I’d known about this quote at Halloween time. It’s a good one for supporting spooky stuff.
(And immediately afterward, Jerome uses it to explain several Scriptural quotes about God dwelling in darkness as well as light, and the majesty and terror of darkness and silence.)
(Translation mostly taken from a footnote in Cain’s translation of St Jerome’s Commentary on Galatians. It is in the CUA Press Fathers of the Church series.)
Aliens in This World 
Fascinating – thank you!
Would it be far-fetched to cross-reference his account of apparent Centaur and faithful Satyr in chapters 7-8 of his Life of St. Paul the Hermit? (Did St. Jerome know St. Athanasius’s Life of St. Anthony? These chapters compare and contrast with chapter 53, there.)
Well, Jerome says at the beginning of his life of Paulus that “both Greek and Roman authors have handed down careful accounts of Anthony”, so I would say yes.