A visit to the Sistine Chapel was mentioned (here) as one of the most interesting achievements that could be obtained by "being on the Internet", I thought it would be worth posting a link.
The vatican.va website offers a few more astonishing sights:
- Pauline Chapel, with a privileged view of Michelangelo's Conversion of Saul (on the left) and Crucifixion of St. Peter (right on the opposite wall);
- Basilica of St. Peter
- San Giovanni in Laterano
- St. Paul outside-the-walls