An early evening casual sex encounter prior to going out, where the parties involved do not see each other the rest of the night, or a location where one goes for such an encounter. 729 describes the hours (seven to nine) during which such encounters typically occur.
"Went to his place, de la 729, then came home and got ready for the party."
"Jenna? She's de la 729, but she's texting me before she goes out."