St. Margarethen Quarry is one of Europe’s oldest and largest quarries. Its sandy limestone has been quarried here since antiquity and continues to be extracted today. It was used to build and restore St. Stephen’s Cathedral and also for buildings around the Ringstrasse in Vienna. Originally formed by a prehistoric inland sea, in the 20th century an abundance of important fossils were discovered in this ancient stone (some a staggering 25 million years old). In 2001 St. Margarethen Quarry and the region of Fertő-Neusiedlersee were added to the UNESCO List of World Heritage Sites.