Now little more than a basin of yellowing grass, the Circo Massimo (Circus Maximus) was Rome’s biggest stadium, a 250,000-seater capable of holding a quarter of the city’s entire population. The 600m racetrack circled a wooden dividing island with ornate lap indicators and Egyptian obelisks. Chariot races were held here as far back as the 4th century BC, but it wasn’t until Trajan rebuilt it after the AD 64 fire that it reached its maximum grandeur.