Toronto's Union Station has been under construction for what seems like forever, but that's because it's more than a renovation; it's a full reconstruction of one of the city's most beautiful and historic buildings.

The extensive work has many wondering what's going on behind all the temporary walls and paths many of us have been walking through each day?

Now, thanks to a new show at the recently relocated Stephen Bulger Gallery, we get to take a peek behind the veil and it's dramatic, to say the least.

Larry Towell: Union Station, on display at the gallery from September 9 to October 14, captures the historic transformation of one of the city's busiest transportation hubs from 2013 to 2015 in photos.

Towell originally had an exhibit planned during the Contact Photography Festival in 2015, but it didn't end up happening.

The world-renowned photo journalist was given special permission to shoot what has been going on far underground as pedestrians moved back and forth everyday to their next train.

According to a release, 900 tonnes of earth were removed by nearly 450 trucks over the course of the shoot. Construction on Union Station started in 2009 and is expected to be completed in 2018 with a new glass atrium, expanded shopping area, and more train concourses.