Photo: Daniel Di Palm / Wikimedia Commons · CC BY-SA 4.0. Cropped; credit added.

A concrete staircase zigzags through a cleft in the Rock of Guatapé, a steep-sided landmark in Colombia’s Antioquia region. The stone walls frame the climb. At the top, the view opens across green hills and branching stretches of water.

The attraction’s operator lists 740 steps to the summit. It’s a sustained stair climb, with the route fitted into the rock rather than spread along a hillside trail. The reservoir beyond it is a much younger addition to the landscape, created for a hydroelectric project in the 1970s.

The rock is also known as Piedra del Peñol. In the operator’s account of its climbing history, Luis Eduardo Villegas López, Ramón Diaz and Pedro Nel Ramirez began ascending its eastern cleft on July 12, 1954. They advanced by wedging wooden steps between the walls. Reaching the top took five days, until July 16.

The modern stairway has concrete flights and railings fitted between rock walls. The number of steps tells visitors more about the outing than a photograph from below can.

The exposed stone belongs to the Antioquian batholith, a large body of rock formed during the Late Cretaceous. Its present shape developed much later. Fractures, chemical weathering and erosion helped sculpt the surrounding terrain, leaving resistant masses standing above lower ground.

An isolated rock can emerge through different processes. Ocean waves helped separate Ireland’s Dún Briste sea stack from its coast; the inland formations around El Peñol developed within a weathered mountain landscape. Their resemblance from a distance hides very different settings.

Researchers have also studied how long these surfaces have been exposed. A Universidad Nacional de Colombia report describes using beryllium-10, an isotope produced in quartz by cosmic radiation, to investigate that history. Such measurements concern the uncovering of rock at the surface, rather than its original formation underground.

The reservoir covered Old El Peñol

When the three climbers reached the summit in 1954, the hydroelectric reservoir wasn’t there. The Río Nare basin would be transformed over the following decades, and Old El Peñol lay in the project’s path.

Residents organized and negotiated over the move. A 95-point agreement dated April 12, 1969, committed Empresas Públicas de Medellín to constructing a replacement town with essential infrastructure. The municipality agreed that the community would leave its old urban center.

The municipality’s history of El Peñol dates a first reservoir stage to 1972. Families moved between May 1978 and April 1979. Houses in the old town were acquired and demolished, and flooding culminated in April 1979.

Guatapé’s urban center survived, although rural areas were affected and its La Aldea neighborhood was lost. Old El Peñol was dismantled and inundated. The water now seen from the rock covers part of a landscape where people had lived and worked, while the replacement El Peñol became their new town.

The cemetery was part of the relocation too. According to the municipal history, the move involved 1,156 bodies from the old burial ground.