Cenotaph for Isaac Newton - by Étienne-Louis Boullée (1728 - 1799)

A hero of the British Enlightenment celebrated by a man of the French pre-Revolution: “utopian designer and speculative architect” Etienne-Louis Boullée.

A classical form, the sphere, without the usual classical trappings.

An empty interior. Just “a sarcophagus at the bottom for the mortal remains of Newton.”

Ridiculously huge. Its dome is “pierced by small holes to shine as new constellations.”

More versions here. None of which were built.

I did say Boullée was Utopian.