I could believe this was a crypt, if it was called “the crypt of…”. (Sailko, CC-BY-SA 3.0)

In the May/June issue of Archaeology, Marco Merola describes the uses put to unused shrines after the fall of Rome. Sometimes they were even looted while in use.

They have also uncovered a shrine dating to the second or third century A.D. dedicated to the goddesses Artemis, Aphrodite of Aphrodisias, and Isis, and the gods Meleager and Dionysus. Several centuries later, the shrine was still in use, despite some of its column capitals having been removed and used as tables in nearby homes. Evidence shows that in the years between the seventh and ninth centuries, a shrine to the god Mithras became a stable…

The place is called the Crypta Balbi not because it was a crypt, but “because the colonnaded portico and theater that enclosed the large courtyard made it dark inside even in broad daylight.”

Of course, several centuries later, the locals may not remember why it was called Crypt of Balbus, merely that that is its name, and there must be a reason. Why, the place is cold even in the summer!

If a shrine can become a stable (and isn’t that just begging for the kind of divine retribution that leads to adventures) after a few centuries, what kinds of uses can shrines and temples be put to millennia later? Your border castle wasn’t built on an old burial ground, it is the old burial ground! And the old burial building used to be a temple of Aphrodite.