That's right. Not only do these stone carvings protect the Cathedral from dark forces (at least according to tradition), they also protect the Cathedral from its arch nemesis — water damage. A gargoyle is essentially an elaborate waterspout that diverts rain away from the Cathedral walls.

Grotesques include all decorative architectural creatures, whether or not they have functioning drainage capabilities. Gargoyles, however, always have drainage conduits. Thus, not all grotesques are gargoyles, but all gargoyles are grotesques.

Ancient Egyptians, Greeks, Etruscans and Romans all employed animal-shaped waterspouts, but the ancestors of the American gargoyles are thought to date back to the 12th century. St. Bernard once disapprovingly wrote, "What is the meaning of these unclean monkeys, these savage lions, and monstrous creatures?" Gargoyles caught on anyway.

While gargoyles appear to cling to the exterior of the Cathedral, they are actually carved from large stones that extend far back into the walls. Gargoyle blocks typically weigh several hundred pounds.

Since Darth Vader does not contain a drainage conduit, he is actually a grotesque, not a gargoyle (see point 2 above). The villainous character was one of four winning entrants in a 1986 contest sponsored by National Geographic World magazine and was placed on the dark, north side of the Cathedral.