During World War 2, an American pilot flying over the Canadian arctic saw something extraordinary. A midnight blue lake, 2 miles across, shaped in a perfect circle.

The Allies kept it a secret, using the lake as a navigation landmark during the war.

But in 1950, photos hit the media, and the lake became a sensation…because it shouldn’t exist.

There were no rivers leading into it, and none leading out. There was not enough liquid groundwater in this frozen landscape to fill it. It was as if the lake had been dropped from the sky.

And in fact, it had. Scientists soon determined it was formed by a huge meteorite.

Its trajectory would have been straight down, striking Earth at 30,000 miles an hour, with the force of 8,000 Hiroshima bombs.

It bored a hole more than 800 feet deep, and pushed up 500-foot high ridges around it, isolating it.

Of course, the natives had known of the crater for centuries, calling it the Crystal Eye of Nunavik -- because it contains some of the clearest surface water on Earth.

Research confirmed that the water came from melting Ice Age glaciers and is only recharged by melting snow and ice.

With no rivers to bring in sediment, the soils on the lake bottom contain mostly dust, pollen and diatoms -- from millennia ago, preserved in the frigid water.

In this way, the Crystal Eye literally lets scientists “see” into the distant past.