The largest manmade stone in the world is in Baalbek, Lebanon. It is known as the Stone of the Pregnant Woman. There are multiple stories around how this stone got its name but the most known one is that women used to visit it and touch it to increase their chances of getting pregnant. This particular stone is estimated to date back at least 2000 years and is estimated to weigh 1650 tons.
See Google Maps images here https://goo.gl/maps/bQVF1MAvE7k and this is good video https://youtu.be/c5LxS7ReRZY