Lonely Planet Writer

Explorers discover ancient cave beneath city of Montréal

An underground chamber believed to be around 15,000 years old has been discovered beneath the city of Montréal. Explorers Luc Le Blanc and Daniel Caron of the Quebec Caving Society made the incredible discovery earlier this month. Having detected a void beneath Caverne de Saint-Léonard in 2014 using dowsing equipment, the pair suspected that a chasm lay hidden underneath the famous cave.

Luc and Daniel inside the cave. Image by Société Québécoise de Spéléologie

“In 2016, we decided to launch a campaign to dig there”, Luc tells Lonely Planet. “However, the limestone was very strong and hard to break. It was quite complicated, as we couldn’t swing a hammer there, so we kind of lost hope. This year though, Daniel and I both retired. He called me and said we should have another attempt. So we returned to the cave and decided to try breaking through closer to the ceiling – there’s a layer of crushed limestone there that’s pretty soft. We were quickly able to get through that layer, and in one single day had opened a ‘window’ that let us see what was beyond. We brought in a ladder, and in another half day emerged into a large chamber, about six metres by three metres.”

Luc explores this newly discovered chasm. Image by Société Québécoise de Spéléologie

The space, says Luc, is beautiful, and very old. “The passages are smooth and vertical; it’s so perfect it looks manmade. On the ceilings are lots of stalactites. In our latitude, they form at a rate of one centimetre per thousand years, and these are 15 – 20cm.” The pair explored the chamber together, although the level of water meant they could only go so far. “Since the passage slopes downwards, as we went further we got deeper and deeper into water. Eventually we got to a point in our canoes where we hit the ceiling.”

Drilling through the limestone wall. Image by Société Québécoise de Spéléologie

Surveying the chamber will continue, and Luc says a cave dive will probably take place too. Though he’s unsure if the chamber will ever be accessible to the public, he says that an innovative new project is underway. “A museum is set to be installed above the cave entrance. There are plans to have glass windows that would give you a view of the cave without going in. There are so many techniques these days that you can use to let people see things like this.” In the meantime, tours regularly run in Caverne de Saint-Léonard, the cave above the chamber. Find out more here.