Happy Birthday, CN Tower! Today Toronto's CN Tower turns 42.

When it was built in 1976, it cost Canadian National Railways $63 million. Back then, the CN Tower was the tallest free-standing structure in the world, at just over 553 metres.

In 1995, the Tower was declared one of the modern Seven Wonders of the World.

Believe it or not, the CN Tower was never intended to be the tallest structure in the world. Its main purpose was to transmit radio signals over Toronto's tall buildings.

So, perhaps it wasn't that big a deal when in 2010, it lost that distinction of tallest free-standing structure in the world when the Burj Khalifa in Dubai claimed the honour at just over 829 metres.

While it may often go digitally deleted in Hollywood films, it's hard to miss its presence in Toronto. One of the best features of the CN Tower is how it acts as an old-fashioned navigation system for people in the city. Not sure where you are? Just look for the Tower and getter a better sense of your location.

Some Fun Facts About The CN Tower

The Tower was completed on February 22, 1974, after about 40 months of work.

The CN Tower weighs 117,910 metric tonnes or 130,000 tons.

Its antenna was completed on April 2, 1975.

1,537 courageous workers laboured around the clock, five days a week, 24 hours a day to build the it.

Lightning strikes the CN Tower about 75 times per year.

The CN Tower tries to be bird-friendly. It dims unnecessary exterior lights during bird migration seasons to prevent injuries to our flying friends.

The CN Tower's 360 Restaurant makes a complete rotation every 72 minutes. So restaurant-goers have an ever-changing view of Toronto, more than 1,000 feet below.