Researchers may have solved a Stonehenge mystery — and raised another. They say its central Altar Stone somehow got to England from Scotland, hundreds of miles farther away than originally thought.

The group Just Stop Oil took credit for the Wednesday afternoon action, which they said was a call on the United Kingdom to stop the use of fossil fuels by 2030.

A seemingly curious alliance of druids, pagans, hippies, local residents and tourists gathered around Stonehenge and greeted sunrise on Wednesday, which is the longest day in the Northern Hemisphere.

Supporters say the tunnel will reduce noise and hide cars for visitors to the prehistoric landmark. Opponents warn of possible damage to the site which archaeologists continue to study.

The massive prehistoric structure "is significantly larger than any comparative prehistoric monument that we know of in Britain, at least," a lead researcher in the project says.