Исаакиевский собор
In 1816, Alexander I of Russia assigned Betancourt to find an architect for rebuilding Saint Isaac's Cathedral. Betancourt promoted Montferrand and, in February 1818, the Tsar approved Montferrand's fifth draft. Betancourt provided Montferrand with an efficient, thoroughly calculated dome design utilizing three interconnected steel domes without any masonry vaults. Cathedral construction was delayed until Betancourt's death; the dome was erected only in 1841.