Cartier Square Drill Hall, Military training facility in downtown Ottawa, Canada

Cartier Square Drill Hall is a 70-metre-long military training hall on the Rideau Canal bank just south of Laurier Avenue, built in 1879 to designs by Thomas Seaton Scott, first chief architect of the Dominion. Its front carries two 43-metre mansard towers, and a parade square fills the interior. A large stores building once stood at the rear, measuring 150 by 70 feet, holding weapons, uniforms and ammunition.

The building was constructed in 1879 under architect Thomas Seaton Scott as a key training center for soldiers preparing for conflict. It served as a crucial facility during major armed engagements throughout Canadian history.

The Officers' Mess, built in the 19th century for the Foot Guards, is where Minister of Militia Sam Hughes declared Canada at war in 1914. It holds the Queen's and Regimental Colours of both regiments, plus an art and regimental silver collection.

The hall stands on the Rideau Canal bank just south of Laurier Avenue, with the former drill field to the west now occupied by Ottawa City Hall and the courthouse. The Parade Square is lent to civilian groups for large dinners and events such as the City of Ottawa Christmas Party and the Ottawa Garrison Ball. During Ottawa Race Weekend the hall becomes a satellite site of The Ottawa Hospital for runners.

The Officers' Mess, built in the 19th century for the Foot Guards, is where Minister of Militia and Defence Sir Sam Hughes declared Canada at war in 1914. It still holds the Queen's and Regimental Colours of both regiments, along with regimental silver and an art collection.