There is a program now (running from May to October) wherein the excavations are open in the evening from 8:30 p.m. to 11:30 p.m. Sunday, Monday, and Tuesday.
As the website says "A moonlight walk among the history of two thousand years ago. The excavations at Pompeii are also open after sunset, thanks to a fixed lighting system which allows a unique, fascinating visit of one of the most beautiful archaeological sites in the world. "
See http://www2.pompeiisites.org/d
n/a
