A Harvard bar would be named after a character in Beowulf, wouldn’t it? Literary allusions aside, Grendel’s Den is the type of low-ceiling, brick-walled basement bar you’ll want to hide in for a few hours on a rainy afternoon. The food isn’t anything special, and the beer and wine list could fit on the back of an index card, but you’re here because it’s cheap (half-off the entire menu during Happy Hour) and comfortable.