Monte Testaccio's use as an amphora dump seems to have ceased after about the 260s, perhaps due to the city's quays being moved elsewhere. A new type of amphora was also introduced around this time to transport olive oil. A need to dispose of these bulky containers remained. Nine buildings in the Rome area constructed in the fourth century have been found to use amphorae as space filler/lightener elements in their concrete portions. One example is the Circus of Maxentius, which was constructed between 308 and 312 at the third mile of the Via Appia: it is estimated that at least 6,000 and more likely as many as 10,000 amphorae were used in this facility. As Peña notes, directing these vessels "toward state-sponsored construction projects for use as space-fillers in concrete vaulting, the "praefectura annonae" could have succeeded in disposing of substantial numbers of highly cumbersome and otherwise useless oil containers, while at the same time reducing the amount of lime, sand and rubble that would have been required to complete these initiatives."