The Colosseum

Occupying a site just east of the Roman Forum, construction started in 72 AD under the emperor Vespasian and was completed in 80 AD under Titus, with further modifications being made during Domitian's reign (81-96).
According to good ol' Wikipedia

Well, we arrived in the evening but it was a balmy 11 degrees out so we took a stroll down to see our first famous landmark. It's beautiful all lit up at night.

Other sights we saw on that first evening were a kerb-side petrol pump, a shop called Sandwich Mania and condom vending machines. Bella Roma!