“Trilithon” is a Greek word that means “three stones”, and describes structures comprising two upright stones with a third laid across the top. The largest trilithons are at Stonehenge, to the South of Salisbury Plain (UK), with single sarsen blocks weighing more than 45 tones.
The tallest upright stone stands 22 feet above ground, with a further 8 feet below ground. The earliest stage of the construction of the ditch has been dated to 2950 BC.
So the marvelous Stonehenge is the largest Trilithon structure in the world.