By Erika Owen
July 22, 2015
Credit: De Agostini/Getty Images

When workers first set eyes on the previously forgotten tunnels beneath the White Cliffs of Dover—dubbed the Fan Bay Deep Shelter—they were in for a historic surprise. The location, which opened back up yesterday for the first time in 40 years, preserved artifacts and graffiti that had been left over from the shelter's heyday during World War II. The passageways, which only took 100 days to carve out, were used to camouflauge German shipping activity within the area. The only thing older than the tunnels on-site are two sound mirrors from World War I—concrete devices used to detect early signs of approaching enemies.

All together, the passageways take up 3,500 square feet, which were frequented by as many as 190 men in its prime. The underground maze was put out of commision in the 1950s, but wasn't fully abandoned—read: filled in with rubble and sand—until the 1970s. To get the space ready for the public, more than 100 tons of debris was removed from the site. It took 50 people (a mix of volunteers, mine consultants, engineers, geologists, and archaelogists) 3,000 hours to ready the tunnels. The area will now host visitors daily until September 6th and then on weekdays through the end of September.

Erika Owen is the Audience Engagement Editor at Travel + Leisure. Follow her on Twitter and Instagram at @erikaraeowen.