<Tr> <Td> Bath, monumental public (Thermae) </Td> <Td> See e.g. Baths of Diocletian </Td> </Tr> <Tr> <Td> Book (Codex) </Td> <Td> First mentioned by Martial in the 1st century AD . Held many advantages over the scroll . </Td> </Tr> <Tr> <Td> Brass </Td> <Td> The Romans had enough understanding of zinc to produce a brass denomination coinage; see sestertius . </Td> </Tr> <Tr> <Td> Bridge, true arch </Td> <Td> See e.g. Roman bridge in Chaves or the Severan Bridge . </Td> </Tr>

Why were roads critical to the success of the roman empire