The ancient stone towers tucked behind the walls of downtown’s Grand Seminaire on Sherbrooke just east of Atwater are among Canada’s most ancient structures. The towers also form part of one of the country's most mysterious places as well.

Some of the city’s very earliest European settlers came from France to establish a settlement on the spot in the 1680s.

Their aim was to promote what they considered a sacred mission to establish a new creed for the New World.

Those missionaries sought to spread their unique vision with First Nations people but they brought most of the details of the plan to their graves.

Those tombs, deep underneath the seminary, are off limits to all but the custodians.

Among those whose remains lie in the crypt, first established in 1661, is Francois Vachon de Belmont who came from Burgundy, France to fund and operate the mission.

The Grand Seminaire has since remained one of the city’s longest-running institutions and is also home to many other architectural treasures, including an alluring chapel, where around 8,000 priests have been trained.

If there is any off-limits place you'd like to see, just send us an email at forbiddenmtl@ctv.ca.

We'll be back with another series in 2013.