Not to be missed place in Italy. It's a World Heritage site. The ticket covers the Palatine Hills visit. There are many things to see in this complex, it's not only the Colosseum. You can buy tickets online and avoid the queue. Note that these are priced differently depending on which areas are allowed. During the summer it's open till about 7 PM.
@vbDev.. Yes it was always thought that the ancient concrete’s durability was based on one ingredient: pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples. This study shows that it goes way beyond that.