June 4 and 5. Discover the city’s architectural treasures during Doors Open Ottawa. With more than 100 buildings on offer, you can tour some of the city’s finest landmarks, some of which are often not open to the public. See the sparkling dome of the Delegation of the Ismaili Imamat, 7 Rideau Gate (the historic guesthouse for visiting heads of state), an assortment of embassies, and other gems. Whether you want the hallowed halls of churches or ultra-modern construction, this annual event takes you to the hidden side of Ottawa design.