Gleno Dam

Gleno Dam is a ruined structure in the Province of Bergamo, Italy, standing at 1,534 meters in the Alps. Two large concrete segments rise from the rocky ground, one tilted forward at an angle and the other upright against the mountain wall behind.

The dam was built between 1916 and 1923 during and after World War I as a water reservoir, and it collapsed on December 1, 1923, sending six million cubic meters of water racing down through several villages. The collapse killed 356 people and led Italy to adopt new regulations for dam construction projects.

The name comes from a nearby village, and hikers walk narrow trails through mountain meadows to reach the concrete walls. On a commemoration day in late autumn, relatives and communities from the surrounding valleys gather for an open-air ceremony where wreaths are laid and stories about the affected families are shared.

The trailhead starts at Pianezza, where vehicles can be parked, and a marked path leads uphill for about two hours to the ruins. During the summer season, a shuttle bus runs from some mountain villages to the parking area to ease the climb.

The design combined arch and gravity dam types in a single structure for the first time globally, a technique that proved unstable. After the disaster, Italy fundamentally changed its planning guidelines for water structures and introduced stricter review procedures for engineers.