Near the centre of the 5000-year-old stone circle known as Stonehenge is a six-tonne stone known as the “altar stone”. It was believed to have been transported from Wales to its current resting place on Salisbury Plain in southern England.
Stonehenge features two types of rocks, the larger sarsens and the smaller bluestones. The sarsens are sandstone slabs found naturally in southern England and weigh 20 tonnes on average. The bluestones are smaller and made of sandstone mixed with volcanic material. They are called bluestones because they look blue-grey when wet or freshly broken.
The largest of the bluestones is the altar stone and it weighs six tonnes and is 5m long. It is thought that the altar stone was installed in the second phase of the construction of Stonehenge, sometime between 2620 BCE and 2480 BCE. At the winter solstice, the setting sun would have shone between the largest of the trilithons (two upright stones capped by a horizontal lintel) and onto the al