In eye sight of Capitoline Hill you can visit the Mamertine Prison. It is a wonderful place to get away in the heat of summertime in Rome and to escape the crowds, but that is not all it is good for. Although the prison is small, it contains a significant piece of history. It was at this prison that held Saint Peter and Saint Paul. For a christian this is a wonderful historical building to see for yourself. Look closely at the cross on the altar because it is upside down, since Saint Peter was crucified this manner. It is said that Saint Peter performed baptisms on his cell mates in the prison.
The prison dates back to the 7th BC and was built as the only prison in Rome originally. One would not want to spend more than a few hours here because you can really feel how gloomy and horrible the conditions of being imprisoned in these confined walls must have been. The prison is also a small museum with Roman pieces on display there.