Den

n. [A-S. den, denn, dene, denu, a valley, a secluded place, a den.]

1. A cave or hollow place in the earth, used for concealment, shelter, protection, or security; as, a lion’s den; a den of robbers.
2. A customary place of resort; a haunt; a retreat; as, a den of misery and vice. “Those squalid dens, . . . the reproach of large capitals.” Macaulay.