A famed landmark of England dates back to the Neolithic era, archaeologists claim it to have appeared between 3000 and 1600 years BC. In roughly 5000 years it's quite a challenge to discover who and why constructed the circle, but the stone structure is believed to have been used for important religious rites by early Britains 4,000 years ago. The landmark became popular again in the twentieth century when modern Britains, and not only, revived pagan festivals at Stonehenge—spring and autumn equinox, and also summer and winter solstice.
These festivals annually draw thousands of visitors: pagans, Krishnaits, druids, representatives of various alternative cultures, and simply curious travellers eager to witness ancient rites, celebrate overnight and watch a splendid sunrise in one of the world's most mysterious places. It's important to know where exactly to stand inside the Stonehenge in order to capture the sun in the proper position right between the rocks, a "stone window" so to speak.
In fact, you can go inside the circle only four times per year—during these pagan celebrations. The access is limited in order to protect the ancient site from possible destruction, as it has already been pretty corroded by rain and wind.
The dates are roughly the same annually—March 21, June 21, September 21, and December 21. However, some tiny deviations are possible—plus or minus a day.