<Tr> <Td> 2006 </Td> <Td> The Porticoes of Bologna </Td> <Td> Emilia Romagna </Td> <Td> </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> The Transhumance: The "Royal Shepherd's Track" (Il Cammino Reale) </Td> <Td> Abruzzo, Apulia, Campania and Molise </Td> <Td> </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Via Appia "Regina Viarum" </Td> <Td> Apulia, Basilicata, Campania and Lazio </Td> <Td> </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> Villas of the Papal Nobility </Td> <Td> Lazio </Td> <Td> </Td> </Tr>

When did the colosseum become a world heritage site