This Weekly Escape newsletter explores the old (and new) secrets of the Paris underground. Also, learn about the health benefits of marriage, and discover a thriving hidden ecosystem.

PHOTOGRAPH BY STEPHEN ALVAREZ, NAT GEO IMAGE COLLECTION

What lurks underneath Paris? Well, it’s almost 200 miles of tunnels that include the city’s legendary catacombs. Despite most of these tunnels being off-limits, so-called “cataphiles” can’t help exploring them via sidewalk manholes and secret trapdoors. With a history of visitors new and old, what secrets do these tunnels really hold?  

PHOTOGRAPH BY ROV SUBASTIAN / SCHMIDT OCEAN INSTITUTE

PHOTOGRAPH BY KEITH LADZINSKI, NAT GEO IMAGE COLLECTION

Planet Earth is home to several spectacular relics from bygone eras—so spectacular that some believe there was extraterrestrial influence. Which of these ancient sites is one of them? 

A. Egyptian pyramids
B. Stonehenge 
C. Sacsayhuamán
D. All of the above

BEFORE YOU GO: Did you know that female octopuses are usually bigger than males? Click here for more octopus facts.

Today’s newsletter was edited and curated by Jennifer Baik and produced by Alisher Egamov. Thanks for reading!