For this week's discussion, I'd like everyone to discuss our virtual tour of the Roman catacombs

For this week's discussion, I'd like everyone to discuss our virtual tour of the Roman catacombs.  

https://www.google.com/maps/@41.9293053,12.5090837,2a,75y,109h,90t/data=!3m6!1e1!3m4!1ssfiLnF1scbgAAAQJOCH0Sw!2e0!7i13312!8i6656

What struck you about the catacombs? What symbols/imagery did you  notice?  What do these symbols mean? How would you characterize their  construction and architecture?  What have you learned about early  Christian Rome that would explain why the catacombs look the way they  do?  

1 paragraph, just asnwer the questions.