The portion of the Roman catacombs open to the public is much smaller than the French Catacombs, although the tunnels themselves go for miles. While the French catacombs were repurposed mining tunnels, these were actually created for the sole purpose of burial. Since these catacombs are also roughly a millennium and a half older than the catacombs in Paris, the bones had long since finished decomposing or been moved. We didn’t see any exposed skeletons during the entire tour.
Pictures were discouraged once we entered the tunnels, so these were taken from my phone without a flash (I didn’t want to damage the painting).
Not included in these pictures: several of the niches in the walls were larger than the others and rounded at the top. One of the other people on our tour asked the guide if these were some sort of special niche for wealthier burials, which seemed like a reasonable assumption. The opposite was actually true. According to our guide, these larger niches were used for the burials of poorer individuals, who were packed in on top of each other before the niche was sealed off.
Also not included in the pictures: deep underground there’s a room where several ancient Christian bishops had been entombed behind slabs inscribed with their names. This room was later turned into a chapel and pilgrimage site, which it still is today. Over the door leaving the room is what appears to be a faded prayer in Latin, of which the only word I managed to “translate” was the final “Amen.”
The catacombs were largely used by Christians, who weren’t allowed to bury their dead inside the city like wealthy Romans, but the tradition of Christians (at least routinely) using these burial chambers to hide during the era of Roman persecution is apparently in question. Here’s a decent article on the topic: http://www.nationalgeographic.com/lostgospel/timeline_06.html