5. Sacsayhuaman Walls
This marvel of architecture was discovered near the city of Cuzco, which was believed to be the capital of the Inca empire.
The wall is made up of limestone blocks, each of which weighs approximately 300 tons.
Aside from accomplishing the Herculean feat of transporting such heavy blocks, what’s truly impressive is the fact that the wall was built without mortar or any kind of cement.
The blocks were carved out individually and packed so tightly together that not even a sharp blade can slide into the space in between.
Scientists have attempted to recreate this wall several times but without success.