Knockturn Alley

Knockturn Alley is a fictional location in J. K. Rowling's Harry Potter series of novels. Leading off of the more savoury Diagon Alley, Knockturn Alley is a dark and seedy alleyway in London to which muggles have no access, and where no respectable witch or wizard ought to be found either. All of the shops and stores in Knockturn Alley are devoted to the Dark Arts[?]; the largest and most disreputable is Borgin & Burkes, which sells sinister and dangerous objects.

Despite its reputation, Hagrid occasionally visits Knockturn Alley in search of Flesh-Eating Slug Repellent and other items which he presumably requires for the care and feeding of the exotic and dangerous creatures to which he tends to become attached..

The name is a pun on "nocturnally".