To ArriveFrom Termini station:
take the metro B and stop at Colosseo Stop (1.50 euros per person). When you get outside the metro, turn to the left and take the stairs on the left that will bring you at via Nicola Salvi. Cross the street and you will be arrived.
From Fiumicino airport:
Take the "Leonard Express" train (16 euros per person) or "Terravision" bus (6 euros per person) that will bring you at Termini station. From Termini you can take the metro for 2 stops (Colosseo Stop)
From Ciampino airport:
Take the "Cotral" bus that will bring you at Termini station. From Termini you can take the metro for 2 stops (Colosseo Stop)