Every Saturday until September 17, the Colosseum will be open from 8:20pm to midnight. (Last entrance is at 10:45pm). It costs €18 to visit the Colosseum and the Colosseum’s “Nero” exhibition, or €23 to also visit the Colosseum underground, with a guide. To book, call +39 0639967700. For more information (in Italian), click here.