The Saint Quirin Chapel was built into the rock in the Petrusse Vally and is considered to be one of the most popular sights of Luxembourg City. The site was first pagan, later became a Christian sanctuary, which from the XI century has been consecrated to St. Quirin. Services were held in the two caves till 1355 when gothic pilgrimage chapel partly hewn into the rock was built, and later, in the XIX century small bell towers and the roof were added. There is a miraculous spring sited near church which reputed to be helpful in curing eye complaints. Much of the interior space of the chapel is situated under the overbuilt road. There are two entries to the church: first from the front door and the second through the rare tunnel way which connects chapel to the incredible underground network of the famous Luxembourg Casements. These Casements were built between the XV and XVIII centuries and corresponded to a network of tunnels that were used as fortifications and could house about 35,000 people. The Luxembourg Casements are a UNESCO World heritage site.