The Ceremonial Guard Changing is one of Canada’s most recognizable military units. For over 50 years the Changing of the Guard has been a top Ottawa attraction, having thrilled thousands of visitors on Parliament Hill, at Rideau Hall and at the National War Memorial.

The Changing the Guard Ceremony

Daily at 10 a.m. on Parliament Hill.
June 28 to August 22, 2015

Also, two others free activities are running:

National War Memorial (National Sentry Program)

Ceremonial Sentries on the Tomb of the Unknown Soldier are expected to resume their duties on August 4 on completion of the renovations to the National War Memorial.

9 a.m. to 5 p.m. – Tomb of the Unknown Soldier
April 9 to November 10, 2015

Rideau Hall

Ceremonial Sentries are posted from 9 a.m. to 5 p.m. at Rideau Hall.
June 28 to August 22, 2015

More information here: http://www.army-armee.forces.gc.ca/en/ceremonial-guard/index.page