http://agathe.gr/overview/the_stoa_of_attalos.html
The Stoa of Attalos The Stoa of Attalos was originally built by King Attalos II of Pergamon (159–138 B.C.), as a gift to the Athenians in appreciation of the time he spent in Athens studying under the ... What he gave the city was an elaborate stoa, a large two-storeyed double colonnade with rows of shops behind the colonnades. ... It was chosen to serve as the museum because it was large enough and because enough architectural elements were preserved to allow an accurate reconstruction; in addition, the northern end stood to the original roof line, allowing precision in recreating the height of the building.