In 1816, the young French designer and architect Auguste Montferrand arrived from Paris. Betancourt incorporated Montferrand to the Building Committee, who also formed part of the team of architects under whose supervision built the cathedral of St. Isaac. Betancourt asked Montferrand to do some sketches of the cathedral. He drew up a small album with 24 pictures, which when presented to the Emperor, were to his liking.

Montferrand spent 1817 drafting the final project. In April 1818, Betancourt gave Montferrand the instructions on how to execute the foundations of St. Isaac. In the summer of 1818, the engineer started to build the scaffolding and the hoisting mechanisms.

Montferrand, in addition, ran under the mandate of Betancourt the drawing office of the Building and Water Works Committee.

The engineer incorporated Montferrand to the project of the Nizhny Novgorod trade fair to translate his ideas graphically onto the plans. As Montferrand was engaged in the construction of St. Isaac's Cathedral in St. Petersburg, his first visit to Nizhny Novgorod was not until July 1822.

When Betancourt died, he left his greatest legacy to Montferrand, his machinery and his devices, which allowed Montferrand to finish the great temple of St. Isaac.

Montferrand designed the project from which they made the impressive 6.85 meters high monument that stands over the tomb of Agustín de Betancourt. Many years later, in August 1852, Montferrand wrote to Alfonso, Betancourt’s son, acknowledging that he had been a simple bricklayer under the command of his father Agustín.