5. The Colosseum in Rome, Italy

Even today, in a world of skyscrapers, the Colosseum is hugely impressive. It stands as a glorious but troubling monument to Roman imperial power and cruelty. Inside it, behind those serried ranks of arches and columns, Romans for centuries cold-bloodedly killed literally thousands of people whom they saw as criminals, as well as professional fighters and animals.

Indeed, it was the amphitheatre's reputation as a sacred spot where Christian martyrs had met their fate that saved the Colosseum from further depredations by Roman popes and aristocrats - anxious to use its once glistening stone for their palaces and churches. The cathedrals of St Peter and St John Lateran, the Palazzo Venezia and the Tiber's river defences, for example, all exploited the Colosseum as a convenient quarry.

As a result of this plunder, and also because of fires and earthquakes, two thirds of the original have been destroyed, so that the present Colosseum is only a shadow of its former self, a noble ruin.

The Colosseum was started in the aftermath of Nero's extravagance and the rebellion by the Jews in Palestine against Roman rule. Nero, after the great fire at Rome in AD 64, had built a huge pleasure palace for himself (the Golden House) right in the centre of the city. In 68, faced with military uprisings, he committed suicide, and the empire was engulfed in civil wars.

The eventual winner Vespasian (emperor 69-79) decided to shore up his shaky regime by building an amphitheatre, or pleasure palace for the people, out of the booty from the Jewish War - on the site of the lake in the gardens of Nero's palace. The Colosseum was a grand political gesture. Suitably for that great city, it was the largest amphitheatre in the Roman world, capable of holding some 50,000 spectators.

Eventually there were well over 250 amphitheatres in the Roman empire - so it is no surprise that the amphitheatre and its associated shows are the quintessential symbols of Roman culture.