Soul of the World – viz of a cube inside the earth whose corners all touch land

See also David Barr's "Four Corners Project" from 1985.

Quoting https://www.aaa.si.edu/collections/items/detail/celebration-... :

"an invisible tetrahedron spanning the inside of the Earth with the outer four corners just protruding from the crust of the Earth. The visible corners are located in Easter Island, South Africa, New Guinea, and Greenland. Barr chose the locations as areas untouched by Western technology and in remote areas in order to bridge diverse cultures."

Yes, they placed little sculptures of the corners at those places.

Video at https://www.youtube.com/watch?v=-juK0PTbAiI

Mathematics at https://deepblue.lib.umich.edu/handle/2027.42/58275 .

There's also Ze Frank's "Earth Sandwich" from 2006, at http://www.zefrank.com/sandwich/ . That only required two points, and had fewer constraints.