The Summer Solstice through Stonehenge on Salisbury Plain. This megalithic stone circle is on Salisbury Plain near Amesbury in Wiltshire, England. The alignment of the stones is thought to have been used to make predictions about certain astronomical events such as solstices and lunar and solar eclipses. For instance, on the longest day of the year (the summer solstice) an observer at the center of the circle sees the sunrise directly over a distant pillar called the heel stone. Construction of this prehistoric monument began over 5000 years ago. The largest stones weigh over 40 tons and stand nearly 7 meters high. Stonehenge is a United Nations World Heritage Site. Wiltshire, England.