Underneath Paris lie dark catacombs, a network of former mines and quarries in which the remains of more than six million people are buried.
Naturally, there's an air of foreboding around them, but an American woman with nerves of steel clearly wasn't daunted by this.
Alison Teal, the self-professed "female Indiana Jones", posted a video on YouTube of her adventure within the deepest parts of the catacombs.
Teal, who hails from Hawaii, documented her journey under the French capital as she searched for a channel of water to paddle her surfboard along. Eventually coming across a water-filled tunnel, she "surfs" the catacombs wearing only a bikini.
She said the clip was filmed as "part of a larger film with an important message".
She added: "Human beings depend upon fresh water for survival and the sea creatures depend upon a healthy ocean for survival - not to mention if the oceans die, we die."
The video has already racked up more than a million views and garnering a mixed reaction, with several people critcising the 30-year-old for "disrespecting the dead."
Watch the video below.