the Perimeter

The 64-mile loop of I-285 around Atlanta, used so heavily as a geographic divider that ITP (inside the Perimeter) and OTP (outside the Perimeter) are standard ways to describe where someone lives or works. Real-estate listings, dating apps, and even old area-code splits leaned on the Perimeter line. Saying 'we are moving OTP' needs no further explanation in metro Atlanta.