The Amphitheatre Flavio of Vespasian, known to all as the Colosseum, is the most popular tourist attraction in Rome, a distinction that makes city officials worry that it might be a potential terrorist target. The huge structure, which is more than 1,900 years old and has for centuries been the symbol of Rome, now has metal detectors at its gates and increased security inside.

The extra precautions mean that tourists will have to wait even longer than before to enter the monument. City officials said that the heightened security, which came into force a month after the train bombs in Madrid, is only a sensible response to the growing threat of terrorism in Europe. Metal detectors are also at the entrance to St Peters basilica at the Vatican.