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: LITERARY SEQUELS 
Clue: "The Restaurant at the End of the Universe" was one of Douglas Adams' sequels to this novel
the hitchhiker\'s guide to the galaxy

Category: HISTORIC EUROPEAN LEADERS 
Clue: On June 15, 1961 Walter Ulbricht assured journalists that "No one intends to build a wall" dividing this city
berlin

Category: AIN'T THAT "GRAND" 
Clue: Term for an extended visit to Europe, once an essential part of a British gent's upbringing

the grand tour