Images courtesy of Stephen Alvarez and taken from the February 2011 edition of National Geographic magazine, which is on the newsstands now. Many thanks to Stephen and National Geographic for sending them our way.

Beneath every urban street lie critical elements of a city’s functionality. Underground train networks exist in many global cities, as do the less glamorous but just as vital parts, such as sewers, water pipes, and the countless cables that fulfil our entertainment needs. However, in many of Europe’s older cities, there’s much more beneath the surface than just wires. Recently published by National Geographic, this fascinating post explores Paris’ catacombs, along with a history of their role in the city:

Paris has a deeper and stranger connection to its underground than almost any city, and that underground is one of the richest. The arteries and intestines of Paris, the hundreds of miles of tunnels that make up some of the oldest and densest subway and sewer networks in the world, are just the start of it. Under Paris there are spaces of all kinds: canals and reservoirs, crypts and bank vaults, wine cellars transformed into nightclubs and galleries. Most surprising of all are the carrières—the old limestone quarries that fan out in a deep and intricate web under many neighborhoods, mostly in the southern part of the metropolis.

Behind the neat stacks of skulls, tibias, and femurs in the Paris catacombs lies a chaos of bones. In the 18th and 19th centuries the city dug up millions of skeletons from over-flowing cemeteries and poured them at night into old quarries.

In a sandy chamber known as the “beach,” a wave rolls across a wall painted (and repainted) by cataphiles in the style of Japanese printmaker Hokusai. Such works can take hundreds of hours—the painting but also the carrying in of supplies.

Paris has thousands of years of history, and Alvarez’s images beautifully capture one previous incarnation of the French capital.