00:35 Stone Monuments in Spain Reappear After Summer Meteorologist Heather Tesch says it was a very hot summer in most of Europe. In Spain, some stone monuments underwater for several decades have reappeared thanks to the heat and a drought.

At a Glance The Dolmen of Guadalperal stone monument was erected 4,000 to 7,000 years ago.

Also called the "Spanish Stonehenge," the monument was submerged in a reservoir in the 1960s.

Drought and record-breaking heat this summer have lowered water levels in a Spanish reservoir enough to expose a megalithic monument known as "Spain's Stonehenge" that hadn't be seen for decades.

The Dolmen of Guadalperal stone monument was erected 4,000 to 7,000 years ago on the banks of the Tagus River near what is now the town of Peraleda de la Mata in west-central Spain.

In the 1960s, the government of Francisco Franco built the Valdecañas Reservoir and flooded much of the area, which is about 100 miles southwest of Madrid.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/SpanishStone2.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/SpanishStone2.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/SpanishStone2.jpg?v=ap&w=980&h=551 800w" > The Dolmen of Guadalperal, also called the "Spanish Stonehenge," is about 16 feet in diameter and has an access corridor nearly 70 feet long. (Facebook/1080 Wildlife Productions)

The dolmen was among the structures covered by the water. Since then, usually only the tips of the tallest stones were visible.

The circular monument includes 144 stones, some of them taller than 6 feet. As with England's Stonehenge, it's unclear who built the monument or what its purpose was.

“We grew up hearing about the legend of the treasure hidden beneath the lake and now we finally get to view them ,” Angel Castaño told The Local, a news site in Europe.

“There certainly may have been treasures buried beneath the stones once upon a time, but for us now, the treasures are the stones themselves.”

Castaño is part of a group trying to save the monument. He told The Local, “Like Stonehenge, they formed a sun temple and burial ground. They seemed to have a religious but also economic purpose, being at one of the few points of the river where it was possible to cross, so it was a sort of trading hub.”

The oval structure is about 16 feet in diameter and has an access corridor nearly 70 feet long. Originally a sun temple , according to La Español, the tall upright stones, called menhirs, were later topped by horizontal stone slabs to enclose the dolmen, or tomb. A wall of pebbles around the dolmen supported an earthen dome.

German archeologist Hugo Obermaier excavated the site in the late 1920s. His research wasn't published until the 1960s.

This past week, NASA published images showing how much the water level in the reservoir had fallen. Spain experienced its third-driest June this century and temperatures were above average in July and August.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/ValdecanasReservoir.gif?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/ValdecanasReservoir.gif?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/ValdecanasReservoir.gif?v=ap&w=980&h=551 800w" > The Operational Land Imager on Landsat 8 acquired images showing the dry conditions along the Peraleda de la Mata coast. The first image was acquired on July 24, 2013, while the second image comes from July 25, 2019. (NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey)

Castaño and Raíces de Peralêda, the group trying to save the monument, would like to see the stones moved to a spot that won't be covered when the reservoir rises again.

“If we miss this chance it could be years before they are revealed again,” Castaño said. “And the stones, which are granite and therefore porous, are already showing signs of erosion and cracking, so if we don't act now it could be too late.”