In the crypt of the Cathedral, two funerary chapels contain the tombs of the bishops of Ottawa.

The Notre-Dame Cathedral Basilica is an ecclesiastic basilica in Ottawa, Canada located on 385 Sussex Drive in the Lower Town neighbourhood. It was designated a National Historic Site of Canada in 1990.

The site was originally home to the small wooden St. Jacques Church built in 1832. This structure was destroyed in 1841 to make way for a larger church, designed by local builder Antoine Robillard and Father Cannon who requested a Neo-classical design.

However, in 1844, after the lower section was completed, the Oblate Fathers took over the parish and Father Telmon was sent from France to finish the construction. Father Telmon decided to redesign it to be a more standard Neo-Gothic structure, a style which was growing in popularity. This left the lower features, such as the main entrance, Neo-Classical, while the rest is Neo-Gothic, for example, the large windows over the doorway features Gothic pointed arches and tracery.

The main structure was finished in 1846. In 1847, it was elevated to a cathedral.

In 1859, Rev Damase Dandurand, a Roman Catholic priest and member of the Oblate Order, designed the two Gothic spires which were erected on the west front of Notre Dame in 1866. In 1849-50, Rev. Damase Dandurand designed the Archbishop's Palace. In 1862-3, Rev. Damase Dandurand designed a choir loft.

The steeples are topped with standard French-Canadian tin and bells. Its exterior is fairly reserved, but the interior is as far more ornate, designed by Georges Buillon. The interior of the church is brightly painted and decorated with carved features, exquisite stained glass windows and hundreds of statues of various religious figures. Louis-Philippe Hébert completed thirty large wooden sculptures in the choir. At the end of the choir, the Holy Family is completed with saints John the Baptist and Patrick, the patron saints of French and Irish Catholics.

James R. Bowes, architect, designed new galleries and improvements, 1875.

In 1879, it was elevated to a basilica and Bishop Guigues was appointed the first bishop and is honoured with a lifesize statue to the right of the Cathedral.

The Basilica is the oldest and largest church in Ottawa and the seat of the city's Catholic archbishop. Its twin spires and gilded Madonna are easily identifiable from nearby Parliament Hill and the surrounding area. The church was recently renovated and restored in the late 1990s. Services are held in both French and English.