At the center of the monument lies the Altar Stone, a massive slab of sandstone weighing around six tons. By analyzing the stone’s mineral composition, researchers now believe the Altar Stone may have come from much farther north. A Mystery Beneath The StonesThe Altar Stone sits at the center of Stonehenge, partially buried under two fallen megaliths. They suggest the Altar Stone was probably moved by sea, following the British shoreline all the way from Scotland to Wiltshire. If the Altar Stone really came from Scotland, it means some of the monument’s stones may have traveled much farther than anyone thought possible.