Piedra Movediza, Balancing granite rock in Tandil, Argentina

Piedra Movediza was a large granite mass that balanced on a hill edge in Tandil and moved each day. A newly installed replica now stands in the same spot while fragments of the original stone rest in the valley below.

The 300-ton granite rock balanced on La Movediza hill until it fell between 5 and 6 p.m. on 29 February 1912, with no direct witnesses. It rolled down the slope and split into three large pieces, now at the base of the hill. Possible causes include vibrations from nearby quarry blasts, vandalism, or a lightning strike in 1848 that flaked off part of its mass. In 1882 owner Ramón Santamarina donated the stone and adjacent land to the Municipality of Tandil.

The name appears on storefronts and business signs throughout town even now. Visitors notice these reminders of the original stone while walking through streets and up the hill.

Climbing the granite steps to the summit takes about 30 minutes at a moderate pace. The replica is always visible while the broken pieces below the hill are often hard to make out.

Visitors used to place glass bottles beneath the swaying mass and watch the motion crush them. This practice demonstrated the daily mechanical force of the stone before it fell.