Piazzale delle Corporazioni

About

Large colonnaded square behind Ostia's theatre, designed together with the theatre in the Augustan period; its double-row Doric portico was added under Claudius (mid-1st century CE), giving it the form -- rows of small rooms (stationes) opening off the colonnade, used as offices by roughly 40 shipping and trade guilds (navicularii, negotiantes) -- that was substantially in place by 117 CE. The black-and-white mosaics identifying individual guilds by trade/origin (grain shippers, Sardinian and North African traders, ropemakers, etc.) that make the site famous today were laid in overlapping phases from the later 1st into the 2nd century CE, so some of the surviving mosaic pavement likely postdates 117; the square, portico, and guild-office function were established well before then. A small central temple (deity uncertain -- Ceres, Annona, and the deified emperors have all been proposed) was added around the end of the 1st century CE, also pre-117.

What happened here

Trade is regulated and everyone is aware of it. Weights and measures are checked against the standards kept by the aediles, and short measure gets you fined and named. Stalls are arranged by trade, with the fish and meat kept to one side and downwind where the town has any choice. Prices swing with the shipping season and are shouted rather than displayed. Much of the meat on sale has come from a sacrifice, so the religious calendar shows up in the supply. Slaves buying for a household argue harder than their owners would. The upper floors, where there are any, are offices and storage let by the town for rent. It opens at dawn and the good produce is gone by mid-morning.

Sources

• https://en.wikipedia.org/wiki/Piazzale_delle_Corporazioni
• https://parcoarcheologicostiantica.it/en/educational-panels/the-area-of-the-theatre/piazzale-delle-corporazioni/
• Russell Meiggs, Roman Ostia (Oxford, 2nd ed. 1973), ch. 6