I'd always known that the modern St. Peter's Basilica was constructed on the site of the original in the sixteenth and seventeenth centuries, but how different one was from the other was never very clear to me. So, being the kind of guy I am, I went and did some digging. Here's what I found:

• This site, while hard to look at because of the bright background, contains a very nice illustration that shows the floor plans of the new basilica, the old basilica, and the imperial circus.
• This is a really nice illustration of what the old basilica probably looked like from the inside, facing the "martyrium", where St. Peter's tomb was located.
• This site provides a nice, simple cut-away view of what the original Basilica looked like. When combined with the floor plan illustration found above, it gives you a good feel for just how different the old church was.
• Rudolfo Lanciani wrote this interesting, if somewhat roundabout account of the history of St. Peter's and the Vatican hill on which it sits.
• This site provides a shorter and more readable history of the basilica, includes links, but doesn't have any pictures.
• Peter's Bones provides a fascinating and detailed account of what, exactly, was found underneath the altar of the basilica during and after WWII when renovations of the crypt underneath it were undertaken.
• This entry in the Catholic Encyclopedia gives a nice summary of the causes and controversies surrounding the destruction of the original cathedral and the creation of the new one.

Archeology and architecture are two of my biggest interests, and the two-thousand-plus-year-old-history of the Vatican hill combines both. I find it fascinating that at one time it was not much more than a swampy old hill, then became the private back yard of the emperors, only to become the epicenter of the largest religion in the world.

Enjoy!