Info from Wikipedia
The El Mocambo is a live music and entertainment venue in Toronto, Ontario. Located on Spadina Avenue, just south of College Street, the venue has played an important role in the development of popular music in Toronto since 1948. It is best known for the 1977 surprise show by The Rolling Stones, which became nationally notorious for the presence of then Prime Minister Pierre Trudeau's wife, Margaret Trudeau, who was partying with the Stones.