The Book of Wonder by Lord Dunsany

The Gibbelins eat, as is well known, nothing less good than man. Their evil tower is joined to Terra Cognita, to the lands we know, by a bridge. Their hoard is beyond reason; avarice has no use for it; they have a separate cellar for emeralds and a separate cellar for sapphires; they have filled a hole with gold and dig it up when they need it. And the only use that is known for their ridiculous wealth is to attract to their larder a continual supply of food. In times of famine they have even been known to scatter rubies abroad, a little trail of them to some city of Man, and sure enough their larders would soon be full again.

Their tower stands on the other side of that river known to Homer -- ὁ ῥόος ἀχεανοίο, as he called it -- which surrounds the world. And where the river is narrow and fordable the tower was built by the Gibbelins' gluttonous sires, for they liked to see burglars rowing easily to their steps. Some nourishment that common soil has not the huge trees drained there with their colossal roots from both banks of the river.