It s one of the most iconic structures in the world. Now, National Geographic presents an exclusive look at groundbreaking evidence that places this ancient monument at the center of one the largest prehistoric religious complexes in the world. Stonehenge Decoded details the discovery and excavation of a 4,500-year-old settlement less than two miles from Stonehenge. Believed to contain hundreds of houses, it is the largest Stone Age settlement ever found in northern Europe. At its center are remnants of a mysterious timber monument arranged in six concentric rings. Now, the excavations and radiocarbon dating reveal that this monument was in fact a near replica of Stonehenge, built of wood and that both circles stood at the same time.