Known as the "Catacomb Saints," the remains of would-be martyrs were entombed below Rome. Photos of them ... were — and sent them across parts of Europe for veneration.

Watch out for that bat behind you,” warned Luca Messina, a civil engineer who moonlights as a speleo-archaeologist with Sotterranei di Roma, Undergrounds of Rome, a local group whose members explore ...

Ukraine is one of only two countries in the "do not travel" advisory, but travellers to the likes of Sweden and Spain are told to "exercise increased caution." ...