what was the discription of the outside of zaroffs house

"Bleak darkness was blacking out the sea and jungle when Rainsford sighted the lights. He came upon them as he turned a crook in the coast line; and his first thought was that be had come upon a village, for there were many lights. But as he forged along he saw to his great astonishment that all the lights were in one enormous building--a lofty structure with pointed towers plunging upward into the gloom. His eyes made out the shadowy outlines of a palatial chateau; it was set on a high bluff, and on three sides of it cliffs dived down to where the sea licked greedy lips in the shadows."

"Mirage," thought Rainsford. But it was no mirage, he found, when he opened the tall spiked iron gate. The stone steps were real enough; the massive door with a leering gargoyle for a knocker was real enough; yet above it all hung an air of unreality."

how is general zaroffs chateau having "a leering gargoyle for a knocker"