VALLE DE VIÑALES, Cuba — Here, the mountains weren’t pushed up from underneath, as mountains usually are. In this national park and Unesco World Heritage site, everything but the mountains fell down. The mogotes, as the islands of karstic limestone are called, are gently domed, like loaves of crusty bread, but the sides seem to have been cleaved off, leaving terrain that drops precipitously to the valley floor.

In the late 1990s, rock climbers found a paradise where the walls of the mogotes are too steep for the otherwise ubiquitous crawling vines and striving trees. Huge overhangs, some 500 feet tall, are covered with chandeliers of stalactites and intermittent blobs and pockets, all perfectly formed for human hands and feet to climb from the bottom of a cliff to its top.

Soon, local residents caught on, and a flourishing climbing scene took hold. Viñales became a top destination for climbers from Europe, Canada and the United States. Hundreds of routes went up the major mountain faces in the valley, and for years visiting climbers had essentially free rein.

No longer.

In late March, even as Pope Benedict XVI called for “authentic freedom” in Cuba before an estimated 200,000 people in Havana, climbers here, a three-hour drive west of the capital, were wrestling with the prohibition of their sport. In an era when the Cuban government has been easing restrictions — allowing private boardinghouses, private restaurants and now the sale of real estate and automobiles — it seems to have moved in a sharply different direction here, threatening the prosperity of Viñales and the future of the sport in Cuba by enforcing a ban on climbing and regulating independent tourism in general.