The Bastion was constructed using the piece-sur-piece method - timbers laid horizontally across each other with tenons cut into the ends and inserted into vertical posts. Nails were expensive on the colonial frontier, so the builders used as few as possible. The logs were squared with basic hand tools: a crosscut saw, broadaxe, adze, auger, and pit saw. Three storeys tall on a masonry foundation, the structure is octagonal in plan - an unusual shape that provided defensive advantages, allowing fire to be directed in any direction. It remains the only freestanding tower structure built by the Hudson's Bay Company still standing anywhere in the world.

McKay used the first floor as his office for the day-to-day management of the coal settlement. From here he oversaw the mines, ordered supplies, and maintained correspondence with Fort Victoria using small "express canoes" that carried messages and passengers between the outposts. Larger vessels like the Beaver and the Otter hauled heavier cargo. Some supplies had to be ordered from England, a round trip that could take two years. The second floor held the arsenal: two four-pound and two six-pound carronades, along with guns, ammunition, and firing supplies. These cannons were fired in welcoming ceremonies when dignitaries sailed into the harbour - and fired into the forest across the water to intimidate First Nations peoples. The third floor provided storage and emergency shelter for Hudson's Bay Company employees and their families.

By 1891, the Bastion had outlived its military purpose and faced demolition. The city of Nanaimo, recognizing the building's historic value, purchased it for $175 and moved it across the street from its original location - to what is now the parking lot of the Dorchester Hotel. Nearly a century later, in 1979, it was relocated again when roads were widened. On December 12, 1985, Nanaimo designated it a local heritage site. The building now serves as a summer tourist information centre with exhibits on its own history, run on behalf of Tourism Nanaimo. The Nanaimo Museum hosts a daily cannon firing at noon during summer months, just a few feet from the Bastion's walls - a tradition that echoes, if more gently, the carronades that once boomed across the harbour.

The Bastion's story begins and ends with the Snuneymuxw people. Chief Che-wich-i-kcan, known historically as "Coal Tyee," opened the door to an industry that transformed the region. The coal he revealed attracted the Hudson's Bay Company, the Company built the Bastion, the Bastion anchored a settlement, and the settlement became Nanaimo. The building that was meant to defend colonial mining interests against the very people who made those interests possible now stands as a museum telling that complicated history. Its image appears on the ship's crest of HMCS Nanaimo, a Kingston-class coastal defence vessel that has served in the Royal Canadian Navy since 1997 - the octagonal fortress still standing watch, in one form or another, over the harbour it was built to protect.