Cala d'Hort is not, at first glance, a beach worth a revolution. It is a modest curve of sand and shingle on the western coast of Ibiza, in the municipality of Sant Josep de sa Talaia, some thirteen miles from Ibiza town and reached by a slow road down through pine and terraced hillside. What sets it apart is what lies offshore. From the water's edge you look straight out at Es Vedrà, the sheer limestone island that rises more than 400 metres from the sea — one of the most photographed views in the entire Mediterranean. To build on the slopes above Cala d'Hort was to build on that view, and that was the line islanders would not let developers cross. The beach later earned a Blue Flag, in 2012, for its clean water.

The threat took shape in the early 1990s. Developers looked at the sparsely populated slopes of the Serra de Ses Roques Altes, above the beach, and saw the perfect place to expand Ibiza's tourist industry: a 420-room hotel, an eighteen-hole golf course, and a desalination plant to supply the enormous quantities of fresh water such a resort would drink. In 1992 the island's green movement, an organisation known as GEN-GOB, began a campaign to stop it. For six years the fight moved through objections and legal wrangles, paper against paper. Then, in 1998, the developers won their permits, and the project was approved to proceed to construction. On the ground, it looked like the end.

GEN-GOB decided that paperwork was no longer enough. In January 1999 the group took its case to the streets, organising a protest march through Ibiza town — and eleven thousand people came. The island's politicians did the arithmetic quickly: those marchers amounted to fourteen percent of the entire population of Ibiza, an unmistakable signal from an electorate that had had enough. The wave of opposition helped sweep the ruling People's Party from power in local elections. By August 1999 the new local government had halted every part of the development. The hotel, the golf course and the desalination plant were dead.

What replaced the resort was protection. In February 2002 the authorities established the Cala d'Hort nature reserve, guarding the beach, the slopes of the Serra de Ses Roques Altes above it, and the incomparable seascape of Es Vedrà as a single protected whole. Where there might have been fairways and hotel wings, there is instead open hillside running down to the sea. The desalination plant that would have fed the golf course was never built, and the water off the beach stayed clean enough to fly a Blue Flag a decade later.

The Battle of Cala d'Hort has become a kind of parable on Ibiza — proof that an island famous for excess can also draw a line. The fight was won not in the courtroom, where the developers had already prevailed, but in the street and at the ballot box, by ordinary residents who decided a view was worth more than a resort. The walk down still ends where it always did, on a small beach looking out at a great rock in the sea. Es Vedrà rises untouched from the water because eleven thousand people once marched to keep it that way.