Archaeologists say the neolithic structure was used for up to 250 years, with more features added every few dozen years.
Residues of fat discovered on pottery near the ancient site may indicate sleds used to move the stones were greased with lard.
Robert Phillips decided the stone should be returned on the eve of his 90th birthday.
Analysis of pig teeth and bones reveals party attendees were coming from all corners of Britain.
Researchers traced the origin of the Wiltshire, England, monument to two quarries in Wales.
English Heritage shares videos from the event.
From hula-hoopers to young lovers, these are the best photos from the U.K's solstice celebrations.
The 4,000-year-old circular monument features wooden posts surrounding burned stones.
"These houses would have been replete with symbolism and meaning, and charged with spiritual energy."
There are rival theories about why the mysterious British neolithic site was built.
This year's summer solstice coincides with the strawberry moon for the first time since 1967.
Archaeologists say the stones, which have earned the nickname 'Superhenge' could predate 5,000-year-old Stonehenge.
Transport secretary Patrick McLoughlin calls proposal "biggest, boldest and most far-reaching roads programme for decades"