Castel Sant'Angelo (English: Castle of the Holy Angel, named after the statue on its top), is a towering cylindrical building in Parco Adriano, Rome, Italy. It was initially commissioned by the Roman Emperor as a mausoleum for himself and his family, and completed in 130AD. The building was later used by the popes as a fortress and castle, and is now a museum.
The Castel Sant'Angelo was featured in Dan Brown's 2000 novel Angels & Demons. The location was the secret lair for the Hassassin and contained the last existing church of the Illuminati.
I took this photo (5 exposures) around 3:30am on December 21st, and the night was warm and crystal clear.