[1][2] At the beginning of the reign of King D. João V there were several deliberations on the possible construction of a sumptuous Royal Palace and a Patriarchal Cathedral,[1] dedicated to Saint Mary of Portugal.
[3] The project was not only intended to create a symbol of the imperial power of the magnanimous monarch but also to celebrate the attribution of the position of Patriarch to the Archbishop of Lisbon Tomás de Almeida (1670–1754) by the Papal Bull «In supremo apostolatus solio» by Pope Clement XI (December 7, 1716).
The initial studies were commissioned by an Italian architect named Filippo Juvarra, who arrived in Lisbon in January 1719 and worked on the schemes until July of that year.
During his stay he also made schemes for the creation of a monumental lighthouse on the Tagus river mouth.
[4] However, the choice of location by the architect (it would be in "Buenos Aires") and the size and architectural style of the building envisioned, inspired by Saint Peter's Basilica in the Vatican,[3] led to the Secretary of State of the King, D. Diogo de Mendonça Corte-Real (1658–1736), to declare the project a show of megalomania.