There are a few way to get to the Tower of Pisa. You can take a bus that will take you directly to Piazza dei Milacoli, where the tower is located. You can also take the train, which runs every half hour. A ticket costs 1,10 €. There is also the option to take a taxi to get to the tour.
Colosseum
The Coliseum can be easily reached by public transport or by foot from anywhere in central Rome.