The name is a corruption of Orto di San Michele, a former monastic garden.  Once a loggia used as a grain market (built by Arnolfo di Cambio in 1290), it was destroyed in a fire in 1304.  It was rebuilt in 1337 by Francesco Talenti, Neri di Fioravante, and Neri di Cione.  Then between 1380 and 1404 the structure was transformed into a church.  The open arcades became windows, and though these are now bricked in, the original Gothic tracery can still be seen.  The austere lines of the large cubic building are softened by the late Gothic marble decoration.  The upper part is in Pietra forte with two tiers of large two-light openings.  14 niches and tabernacles with statues are set into the outer walls (particularly famous are Ghiberti's St. John the Baptist (1414-1416), Verrocchio's St. Thomas (1464-1483), Nanni di Banco's Four Crowned Martyrs (1408), and the copy of Donatello's St. George (1416).  Inside the church is the imposing Tabernacle by Orcagna, in flamboyant Gothic style (1355-1359).