The Bank of Montreal | Banque de Montréal is the oldest bank in Canada (1817). In 1847, the bank's new head office was built on Rue Saint-Jacques at Place d'Armes. It's no longer the bank's head office but it's still used as a bank. There's also a museum inside with exhibits displaying old money and other banking memorabilia.
This area is pretty peaceful at night making it quite nice to walk around.