The Coliseum is a place where you must arrive early; say 9am, if you don’t want to wait in long queues. This also applies for the St Peter’s Basilica, Vatican Museum and the Sistine Chapel.
The best tip of all for Rome is NOT to exchange your SEK to Euros in one of the numerous bureaux de change. One by the Trevi Fountain sold EUR for SEK 9.80, another by the bus and train station, Stazione Terminale, took SEK 10 exactly! Compare this to FOREX, who sold EUR at 9.26 the very same day.