 A horreum was a type of public warehouse used during the ancient Roman period.Although the Latin term is often used to refer to granaries, Roman horrea were used to store many other types of consumables; the giant Horrea Galbae in Rome were used not only to store grain but also olive oil, wine, foodstuffs, clothing and even marble.By the end of the imperial period, the city of Rome had nearly 300 horrea to supply its demands.