 In October 2007 , a time capsule was found inside the stone ball base of a cross , in the southern bell tower of the cathedral . It was placed in 1742 , supposedly to protect the building from harm . The lead box was filled with religious artifacts , coins and <unk> and hidden in a hollow stone ball . The ball was marked with the date of 14 May 1791 , when the building 's topmost stone was laid . A new time capsule will be placed in the stone ball when it is closed again . 
