EMPIRE great market (5.47, 5.48) and later the Baths of Caracalla and Diocletian (5.73 5.74). These great buildin gs were, however, simply inserted in the urban fabric that had grown up over the centuries. The result was a fortuitous mixture of grandiose public buildings and plain or nondescript privately owned tenement blocks (insulae) on the low willdilly streets where the mass of the population lived (5.39) Nevertheless, there were pockets of systeinalic planuing. According to the Roman historian Tacitus, broad streets were laid out on a grid plan over the area devastated in the great fire of Nero's reign in 64 AD. Surviving buildings at Ostia, the port of Rome, give some indication of what this Roman scheme must have looked like: wide streets lined with covered porticoes and small shops, and orderly insulae of brick-faced concrete up to five stories high, arranged around central courtyards. Only in the provinces where new towns could be founded were Roman