Submerged Bridge in Spanish Cave Built Nearly 6,000 Years Ago

Researchers recently discovered that a submerged bridge inside a cave is much older than previously believed. The limestone bridge, located inside Genovesa Cave on the Spanish island of Mallorca, was actually constructed nearly 6,000 years ago—challenging assumptions about ancient human activity in the Mediterranean.

In 2000, researchers came across the submerged bridge for the first time during a scuba-diving expedition inside Mallorca‘s Genovesa Cave, which is now flooded. Made of heavy limestone blocks stacked on top of each other, the bridge measures 25 feet long. At that time, researchers determined that the bridge was approximately 3,500 years old based on pottery fragments found in the area.

However, recent studies on rising sea levels in the area inspired researchers to revisit the submerged bridge. “It was only in the past four years that we finally gathered the data needed to address this longstanding research topic and better estimate the arrival time of humans in Mallorca,” said Bogdan Onac, lead author of the new study and professor of geology at the University of South Florida. The research team’s updated analysis determined that the bridge was built approximately 6,000 years ago—meaning humans inhabited the area much earlier than previously thought.

Researchers Analyzed Sea Levels and Mineral Deposits

The research team reconstructed historic local sea levels and analyzed mineral deposits to determine the true date of the submerged bridge’s construction. Shifts in coloration showed historical changes in sea level, and calcite encrustations formed on the bridge as the water rose. A “distinct light-colored band” along the upper portion of the bridge matched the same level where mineral deposits formed when the sea level was at a standstill. This indicates the bridge was constructed earlier than 5,600 years ago.

“The sea level sat there for a couple hundred years, allowing the mark to happen,” Onac explained to CNN. “The time when the bridge was constructed also shows that people were utilizing this cave much earlier than previously thought, closing the gap between eastern and western Mediterranean settlements.”

The research team believes the submerged bridge inside Genovesa Cave was used by ancient humans for 400 to 500 years before rising sea levels prevented its use. They also have some theories about the function of the cave: “Humans may have used the area near the cave entrance, a large collapse chamber, for living,” Onac told CNN. “The purpose of crossing the lake to access that chamber remains unclear; it could have served as a refuge, place for rituals, or as a storage place, keeping food out of Mallorca’s hot days.”

Mallorca is close to the eastern shore of Spain’s mainland and one of the larger Mediterranean islands. It was also one of the last islands in the area to be inhabited by humans. Researchers are still trying to determine why Mallorca was settled later than the eastern islands in the Mediterranean Sea. The island’s hot and dry climate, lack of farmable land, and limited natural resources may have deterred early settlers. “In contrast, other islands had more favorable environmental conditions and abundant resources, such as minerals and livestock, which made them more attractive,” said Onac.