The unbuilt praise for Issac Newton: Étienne-Louis Boullée's cenotaph.

From Wikipedia:

"Born in Paris, he studied under Jacques-François Blondel, Germain Boffrand and Jean-Laurent Le Geay, from whom he learned the mainstream French Classical architecture in the 17th and 18th century and the Neoclassicism that evolved after the mid century. He was elected to the Académie Royale d'Architecture in 1762 and became chief architect to Frederick II of Prussia, a largely honorary title. He designed a number of private houses from 1762 to 1778, though most of these no longer exist; notable survivors include the Hôtel Alexandre and Hôtel de Brunoy, both in Paris. Together with Claude Nicolas Ledoux he was one of the most influential figures of French neoclassical architecture
Geometric style"


Boullée promoted the idea of making architecture expressive of its purpose, a doctrine that his detractors termed architecture parlante ("talking architecture"), which was an essential element in Beaux-Arts architectural training in the later 19th century. His style was most notably exemplified in his proposal for a cenotaph for the English scientist Isaac Newton, which would have taken the form of a sphere 150 m (500 ft) high embedded in a circular base topped with cypress trees. Though the structure was never built, its design was engraved and circulated widely in professional circles."

The Cenotaph (or tomb) interior fully lit, Boullée's design was to have the interior of the structure complete a full solar cycle.