Now a huge basin of dusty grass, Cir­co Mas­si­mo was ancient Rome’s largest char­i­ot race­track, a 250,000-seater capa­ble of hold­ing up to a quar­ter of the city’s pop­u­la­tion. The 600m track cir­cled a wood­en divid­ing island with ornate lap indi­ca­tors and Egypt­ian obelisks.