 The biggest were enormous, even by modern standards; the Horrea Galbae contained 140 rooms on the ground floor alone, covering an area of some 225,000 square feet (21,000 m²).The first horrea were built in Rome towards the end of the 2nd century BC, with the first known public horreum being constructed by the ill-fated tribune, Gaius Gracchus in 123 BC.The word came to be applied to any place designated for the preservation of goods; thus it was often used refer to cellars ("horrea subterranea"), but it could also be applied to a place where artworks were stored, or even to a library.