This is where the ostensible bones of St. Peter were found and the candidate for the "troparion" or trophy of Gaius. Constantine had gone through a massive amount of effort to put the basilica on top of the Vatican hill, and to align its main altar directly over a grave in the Roman necropolis.
You're right. This is not the best title. The original news story (linked above) is to Bloomberg which is a blocked source. They entitled their news story: Vatican Necropolis Gives Up Secrets After Escaping Construction
I searched other news sources but the best I could find were the photographs released by the Vatican which are posted above. CNN and USA Today are now catching up. BTW - those terracotta pipes projecting from the ground, are funnels where visitors would pour honey and other foods down to the deceased.
Here's one more photo.
In this undated photo provided Monday, Oct. 9, 2006 by the Vatican Museums, a mosaic floor is seen in an ancient necropolis unearthed at the Vatican.