The disrupted historical background of the evolution of Santiago’s Cathedral can also be seen through its architectural structure. Although, there are several stages that the Cathedral’s layout has gone through related to natural and human events, we can, however, differentiate four significant stages that in our opinion and for better understanding, the architectonical development of this building can be divided into: The first initial stage, ranges from its construction in 1541, including innumerable failed attempts to keep it standing, until the 1730 earthquake; a second stage entails significant modifications made by Matías Vásquez de Acuña; a third stage, relates to the contribution made by the architect Joaquín Toesca; and a fourth stage, which covers up to the final transformations performed by the architect Ignacio Cremonesi. Thus, the temple evolves in its construction from the use of adobe, to quarry stones, and from brick to structured concrete; and the spatial development goes from a small internal post and dintel place to the building comprising three naves, the central one being the largest, finished off by cannon vaults and its walls completely covered to include abundant decoration.

In its first stage, once the city of Santiago was founded and the land was divided in order organize the city, the current cathedral’s works are immediately performed, erecting the church that according to Spanish customs brought to South America by the conquistadores, had to be located next to the main colonial buildings at the Plaza Mayor (Main Square). Thus, land is designated on the north-western side of the square, so that the temple had to be built according to projected drawings, and it had its main entrance going out to the actual Cathedral Street. It is known that this first provisory rustic building, made from adobe and with a straw roof was totally destroyed by a fire started by the Cacique Michimalonco. Later, after a series of unfortunate events through time, the temple is re-built over and over again. Earthquakes and fires were accountable for the destruction of these buildings and once the re-building works began after these disasters, they applied new materials, techniques and terminations that as time elapsed became part of modernizing the building.

The 1730 earthquake was very significant, since starting from this disaster begins the construction of what we know today as the Cathedral of Santiago. In this project, stone masonry was considered for the foundations due to economic and seismic reasons and a different ashlar masonry stone was used for building the perimeter walls, pillars and arches. The person in charge of this project was the builder Matías Vásquez de Acuña who gives the temple the current spatial dimensions, forming the Basilica structure in three naves and is responsible for changing the location and direction of the building, which up to that time had an east-west direction, and its entrance, in turn was located on the Arms Square. He died while working in this building, finishing two-thirds of the temple construction. The construction is then allocated to Francisco Antonio De Barros who, due to health reasons, also stops working on the project. In 1780, the architect Joaquín Toesca takes on the direction of the works.

The Italian architect Joaquín Toesca combined two important aspects: he had to continue with the inconclusive work of Vásquez de Acuña by following the drawings projected previously by the Jesuit priests with the application of his own innovating architectonic ideas brought from the old continent and influenced by the new reigning neoclassic currents in architecture and decoration. He re-designs the Cathedral’s façade into a “Toscan” style (called “Doric” by the reigning classicism of the end of the XVIII Century), using columns, fluted adjacent pilasters, circular pediments that crown the entrance doors and topped by huge semicircular arches. He also builds the side chapel and the Archbishops’ Palace in the same style. Moreover, he designs the western tower of the side chapel, but dies before he is able to build it, which is why he entrusts this work to his disciple, Juan José de Goycolea. The building was also topped with a balustrade in its cornice and a triangular pediment.

Afterwards, the project is taken up by a series of successive professionals, who carry out different changes and remodeling. Eusebio Chelli unifies the Cathedral’s façades and the side chapel and Juan Murphi builds the two-body tower located on the northern part of the side chapel, in 1874.

The last stage, and the one in which the most important transformation is performed and is still standing to date, corresponds to the one carried out by the Italian architect Ignazio Cremonesi, hired by Archbishop Mariano Casanova, in 1898. He develops the final transformation of the temple’s east façade that goes out towards the Arms Square, although he respectfully maintains the previous work done by Toesca. The two main towers over the east façade and the central dome are then built, which were constructed with steel and structured concrete construction technology. The northern and western walls, which were built with completely naked stone, were covered with brickwork and whitewash mortar, so that it appeared like a “second skin” and the balustrade over the northern wall perimeter is used to conceal the new coating. He makes the small windows existing up to that time bigger, using them to create stained glass windows. In the church interior he had the roof wood framing demolished and built the cannon vault in the central nave.

Afterwards, in 2000, due to the extension of line 5 of the Santiago subway, the voussoirs of the arches were modified in order to transform their structure, thus keeping the exterior image that can be appreciated today.