At the end of the last ice age, glaciers rapidly receded across Canada, putting so much pressure on the land below that solid rock split apart. Perhaps nowhere is that more evident than a newly discovered cave system some 20 feet below Montreal, Quebec. Suspecting that a cave beneath a Montreal park expanded wider and deeper than anyone knew, Luc Le Blanc and Daniel Caron of the Quebec Speleological Society dug through soft limestone in October and found the "incredible" chamber, per the CBC. On the other side was a network of caves stretching the length of two football fields. It was shaped roughly 10,000 years ago as rock was pulled apart by glaciers, evident in rock wall outcrops that would fit like puzzle pieces into those across the expanse, littered by stalactites and stalagmites formed over millennia.
As Le Blanc tells the BBC, it's "the kind of discovery you make once in a lifetime." But it wasn't without challenges. Once through the limestone ceiling of the network, Le Blanc and Caron traversed a rock wall and found themselves at the end of a sloping passageway halted by deep water. "The walls are perfectly vertical. It's just beautiful," Le Blanc says, per the CBC. "The walls just opened through the pressure of the glacier above about 15,000 years ago," he adds, though officials put the date at 10,000 years ago. Le Blanc and Caron have since used a boat to explore all but 50 yards of the cave network. National Geographic reports they're waiting until February, when the water table lowers, to explore it in full. That's something the public will also be able to do, once efforts are made to protect the stalactites and stalagmites, per the CBC. (See what cave stalagmites reveal about Iran.)