In 2005, Pascal Sombardier discovered the largest natural arch in the Alps, Tour Isabelle or Tour Percée, with a span well over 90 feet (30 meters). He revealed the find to the world a year later in a book entitled Chartreuse Insolite, with a cover photo that triggered a passion for arch hunting across the region. In the following years, over 70 arches were added to the list in Chartreuse alone. The Chartreuse Mountains, a limestone massif in France, is a reasonably small range but boasts some of the most beautiful…
