Explorers have unearthed a massive Ice-Age-era cave network below the Canadian city of Montreal, according to new reports.

Daniel Caron, who made the startling find along with fellow cave scientist Luc Le Blanc, was awestruck to discover a place to untouched by humanity lurking a mere 30 feet below Montreal’s busy streets.

“Normally you have to go to the moon to find that kind of thing,” he told the Canadian Press.

Even as the city of 1.75 million grew since its founding in 1642, the cave network — formed between 10,000 and 15,000 years ago — remained hidden right under Montrealers’ noses.

“They’ve dug sewers and made basements, but no one had ever seen them,” La Blanc told National Geographic.

Caron and Le Blanc made the find while exploring the already-known St. Léonard cave beneath the Pie-XII Park in the city’s north.

The pair began hunting in 2014 for undiscovered passageways long rumored to be hidden there, using a radiolocation kit and even pseudo-scientific “divining rods” — a Y-shaped device that is supposed to find water — to look for liquid-filled caverns behind St. Leonard’s walls.

The pair found a promising fissure in one wall in 2015 and brought in fellow cave scientist François Gelinas to feed a camera through the crack, revealing a massive, undiscovered cavern on the other side.

It took nearly two years before the team could step foot in the chamber, because the cave’s limestone walls required heavy-duty drills to break through.

When they breached the rock, they found a cavern roughly 10 feet wide, 20-feet tall and stretching back about 700 feet with other passageways splitting off.

“The walls are perfectly smooth and the ceiling is perfectly horizontal,” Le Blanc said, explaining the cavern walls likely got their smooth finish when giant ice sheets receded during the last Ice Age up to around 15,000 years ago.

The far end of the cave dips down into Montreal’s water table, requiring spelunkers to take a dive to go any further, and the side passages also remain unexplored, according to Le Blanc.

“It keeps going. We haven’t reached the end yet,” he told CBC News.