Centuries later in Paris, catacombs emerged as a creative and discreet solution to a dire public health problem.

BBC: Exploring the history of catacombs

Of the sites below, only the Paris and Odessa Catacombs have small stretches that are legal to visit.

BBC: Discovering an unseen urban underworld

The catacombs are a by-product of Paris' early development.

CNN: Loving life in Paris' Empire of the Dead