On the corner of a cross street in Dartmouth, Nova Scotia, an oddity: a cannon, its muzzle bent sits atop a short pillar. Cars drive by, people walk past, few seem to notice. Not surprising, after all it's always just been around.

The mundane relic got here as a result of the greatest single disaster in Canadian history.

December 6, 1917.

It's a date anyone who's lived in Halifax knows well. In many families, like my own, it's a day that continues to prompt discussion.

Canada had endured three years of the First World War.

Halifax, being on the east coast, was the point where troops and goods left for the front, making the city a bustling centre. Ships of every size came and went, thousands of soliders, sailors, workers and their families crammed homes filling the hillside above the warves, warehouses and factories at water's edge.

Just before 9 a.m., two ships -– the Mont Blanc, filled with explosives and headed up the harbour, and the Imo, a Norwegian ship moving in the other direction –- collided in the Narrows.

The Mont Blanc caught fire and the attention of people in the city's north end. They went outside or to windows to watch blaze, unaware that in an instant it would unleash a blast unlike the world had ever seen.

Thousands of tonnes of explosives of went up creating the largest man made explosion before the advent of the nuclear bomb.

It destroyed everything kilometres around.

Nearly 2,000 people were killed, fires burned, houses collapsed. A thousand people were immediately blinded by flying glass. Almost half of Halifax was homeless. Entire families died together, others were changed forever.

A clock atop city hall suddenly froze at 9:04:35. It remains that way to this day.

People immediately suspected the Germans had invaded.

Aid poured in from across Canada and significantly from Boston. To thank them for their help, for the past few decades, Nova Scotia’s have donated a tree, the centrepiece of the city's Christmas display.

Today, a century on, the legacy of the explosion lives on.

From Canada’s first planned neighbourhood of homes, the hydrostone, built for survivors, to the C.N.I.B, created to help the blind, to that cannon, sitting three kilometres from the harbour where it was blown from on what was the darkest day our country has ever experienced.