There are myths about the construction of Stonehenge, but relating it to the summer solstice makes some sense. The answer to the question about building Stonehenge is easy when its summer or winter solstice. As the rising sun on summer and Winter solstice aligns perfectly with the standing stones. This may be one of the reasons to constructing the monument but there is more to be found yet.
Another question which circulates on forums, communities and Search Engines about the longest day is: why people go to Stonehenge on the day?
Modern Druids and Pagans believe that their ancestors had built the monument to worship their gods. Therefore they come at Stonehenge to the believed temple for worship. But many come to witness the rising sun of summer solstice. Many, who witnessed the moment, express it as magical. When the sun appears exactly above the Heel stone facing towards northeast, is one of lifetime experience.
There are many things to keep in mind before going to Stonehenge on the day. Personal convince is not allowed, environment preservation is kept in mind and much more rules to be followed. Advance tickets needs to be booked for entry. Public transport is preferred and recommended for visitors so as to keep environment safe and clean. Trains and buses regularly pick and drop visitors near to the site. Within a 20 kilometers circle to the monument there are many campsites, hotels and guesthouses available. But the bookings need to be done in advance.
Have a unique experience of sun worshiping and sun rising at the oldest monument of the world this year. You may read more about interesting summer solstice festivals here.