Notre-Dame Cathedral Basilica is Ottawa's oldest and largest church, built between 1841 and 1885. This neo-Gothic Catholic church features twin 55-metre spires and a stunning interior filled with wood and gilded carvings. The inside contains over 30 intricately carved statues, exquisite wooden mosaics, and stained glass windows. A National Historic Site, it remains an active parish church. Located directly across from the National Gallery, making it easy to combine both visits.