Question: Master Gerhard was the first master mason of a cathedral that was declared a World Heritage Site in which year ?
Sentence (from "Cologne Cathedral"): Cologne Cathedral (German: "Kölner Dom" , officially "Hohe Domkirche Sankt Petrus ", Latin: "Ecclesia Cathedralis Sanctorum Petri" , English: Cathedral Church of Saint Peter) is a Roman Catholic cathedral in Cologne, Germany.
Relevant evidence: No