Stoa Basileios (Greek: στοά βασίλειος), meaning Royal Stoa, was a stoa constructed in Ancient Athens in the 6th century BC and substantially altered in the 5th century BC. It was located in the northwest corner (known as "the Herms" because of the great number of Hermae set up there) of the Athenian Agora. The stoa was built in the Doric order and it measures 18 by 7.5 meters. Its facade carries a plain Doric frieze. Its Doric exterior includes 8 columns, while its interior space includes four columns. The modifications of the fifth century BC add two small porches to the archaic structure.