You’ve probably heard of Stonehenge, but did you know there’s something called Torontohenge?

Toronto’s version has little to do with the prehistoric monument of incredible archeological significance.

Torontohenge is a unique event that happens but a few times a year.

And the final day to catch it in 2016 is on Tuesday.

Here’s everything you need to know about Torontohenge:

So what is it?

When the clock strikes 6:18 p.m. on Tuesday, people will have the chance to watch the sun bathe Toronto’s east and west streets in warm orange and red light as the sun sets. The sunset lines up perfectly with east and west streets just twice a year, and Tuesday is the last chance in 2016 for observers to catch the unique sight.

Why is it called Torontohenge?

Stonehenge, the 5,000-year-old monument in the southern United Kingdom, is believed to have been a prehistoric temple aligned with the movements of the sun.

“Thousands of years ago, people used Stonehenge as a giant calendar, as it was built to lineup with the sunrise on the Solstice,” said Marciniak.

“This is the same idea. We’re still fascinated by the movements of the heavens.”

Why is Torontohenge a big deal?

It’s not just the fact that it only happens twice a year that makes the event impressive, said Ryan Marciniak, an astronomy researcher at the Ontario Science Centre.

“When you live in a big city, you don’t get to see many sunsets unless you’re living really high up in a condo,” he said. “It’s great if you’re a pedestrian, because you get to see a beautiful sunset in the city, which is usually a lot of trouble with all the tall buildings.”

Drivers heading west through the city may not find it so beautiful.

“If you’re driving along the city streets, you’ll get a good 10 minutes of bright sunlight in your eyes before it makes its way down,” Marciniak said.

Does it happen anywhere else in the world?

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Toronto’s city grid, where streets are largely aligned going north-south and east-west, lends itself perfectly to this phenomenon, but it’s certainly not only the only cityscape that does.

These kind of “henges” are all over North America, including New York City, Montreal and Chicago. New York’s “Manhattanhenge” falls on a different date than Toronto’s.

“It depends on the layout of the cities, whether they stick to cardinal directions, and when it actually happens depends on the latitude of the city,” said Marciniak.