From Project Athinai
The Leokoreion was a small square enclosure dedicated to the daughters of Leos who had been sacrificed in earlier times to save the city from plague. This sanctuary was erected in front of the south end of the Stoa Basileios around a rock outcrop considered sacred at the north-west corner of the Agora. In 480 BC, this Crossroads Enclosure was badly damaged by the Persians occupying Athens and was repaired around 450 BC.
The enclosure consisted of upright slabs of poros capped by crowning members. A well with a poros mouth stood immediately on the north of the enclosure and was probably associated to the cult practised there.
American School of Classical Studies at Athens; The Athenian Agora: A Guide to the Excavation and Museum, 1990
Camp, John M.; The Archaeology of Athens, Yale University Press, 2001, p. 261