The classical (non-quantum) theory of gravity was developed by Einstein
around 1915. Gravity is described by the geometry
of spacetime, which is dynamically determined by the distribution
of energy and momentum.

The is an elegant mathematical description, based on the Equivalence
Principle, in terms of differential geometry.

Experimental successes of this theory:

light bent by sun

perihelial precession of Mercury

spin down of binary pulsars from gravitational radiation