If you are interested in visting the Roman National Museum sites (Palazzo Massimo Museum and the Octagonal Room of the Baths of Diocletian), the Colosseum, the Palatine Hill, the Baths of Caracalla, the Tomb of Cecilia Metella and the Villa of the Quintilii, perhaps you should consider purchasing the Roma Archaeologia Card. The card will get you into all of the above-mentioned sites for 20 Euros. It saves you a few Euros and it will save you waiting in line at the Colosseum, which is worth paying any price! Buy the card at the entrance to the Palatine Hill (near the Forum Romanum). If you don't plan on visiting all of the sites that the card covers, you can still avoid the long line at the Colosseum without purchasing the card. As luck would have it, the regular entrance fee to the Palatine Hill also includes entrance to the Colosseum.