Tucked behind the stunningly plain white façade of the Church of Sao Roque in Portugal’s capital city, Lisbon, is a treasure-filled chapel that is widely recognised as being the most expensive chapel in the world. Built using precious materials as gold, silver, ivory, deep blue lapis lazuli and the brightly grained gemstone, agate, Capela de Sao Joao Baptista or the Chapel of Saint John the Baptist, was originally constructed in Rome on the commission of King John V in 1741.