To give the impression of climbing down a long flight of stairs to the catacombs, Lugosi and Brent walk in circles around the same few steps. The effect is given away when their timing gets off and Brent, who's supposed to be ahead of Lugosi, is seen popping into frame behind him.
As the General and Count walk the stairs down to the catacombs, the stone walls (painted on flats) flutter back and forth