Interesting but... You should allow more possibilities for each valid answer. Giza, Gizeh, Giza Pyramid, etc didn't work. Having to type out cathedral is a bother. Enabling Stralsund for St Mary's and Hamburg for St. Nicholas would be nice and more informative. More crucially, the list is wrong. Beauvais Cathedral was the world highest building for a few years (1569–1573) before its tower collapsed and Old St Paul's Cathedral in London was the tallest building in the world during the 13th century.