The 72-hour Roma Pass allows the purchaser free entry to the first two attractions; the 48-hour Pass, a single attraction. Access to subsequent sites are discounted.
Probably more out of a sense of justifying our “sound” financial judgement about the Roma Pass than any real desire, we decided that we should see a second attraction, another museum perhaps; the single free admission already earmarked for the Colosseum/Roman Forum/Palatine Hill.
The list of museums for which the Roma Pass offered reduced costs were lengthy and varied. The Museo Nazionale degli Strumenti Musicali showcased unique musical instruments from the ancient world up till the 18th century. The topographic transformations and various aspects of cultural, social, and artistic history of Rome from the sixteenth to the nineteenth century were featured at the Museo di Roma. In the end, we went with the Galleria Nazionale d’Arte Antica a Palazzo Barberini because of its proximity to the other places we had planned on seeing.