You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: PRESIDENTIAL FIRSTS 
Clue: The first president to cross the Atlantic Ocean while in office, he did so to meet with other world leaders
wilson

Category: ANATOMY 
Clue: Organ whose workings were the subject of a 1604 work by Johannes Kepler
the eye

Category: THE WORLD OF CINEMA 
Clue: In 2006 "The Nativity Story" became the first film to have its world premiere in this country, in Paul VI Hall

vatican city