No, it wasn't an alien invasion. Over the weekend, large ice circles appeared on Ottawa's Rideau Canal that left locals mesmerized by their mysterious appearance.

But it turns out the frozen 'crop circles' isn't anything to worry about.

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The National Capital Commission explained the ice patterns were created when using pumps to flood the surface.

Despite the canal freezing every winter, most locals may have never seen this sight before.

Large sections of the ice are dotted with circles, with each shape having a unique design.

The contrast between the dark frozen surface and white snow is rather striking and can be seen best at night.

According to Ottawa Tourism, the rare occurrence "needs the perfect combo of water, temperature, ice and snow."

The Rideau Canal isn't ready yet for skating so if you are eager to lace up your skates, you can head to the Rink Of Dreams at City Hall instead.