Just as the Covered Plaza is the most striking open space of the Ciudad Universitaria, the Aula Magna is the foremost exponent of its inner areas. With a capacity for 2700 people, it is the campus’ most spectacular place. One is astonished on discovering its light and color, resulting from the collaboration between Villanueva and Alexander Calder. Its fan shape did not particularly favor acoustics, but thanks to Calder’s «flying saucers», the problems were solved. Calder’s participation was a unique experience for Villanueva and the others involved and a gratifying one for the artist, who said «It is the best moment of my art». In the case of Las Nubes, Fede­rica Palomero says that «the synthesis is absolutely organic: this work could not exist elsewhere, and it would be a different building without it». With highly praised acoustics, the most amazing thing is that these Calder «stabiles» managed to turn weakness into strength. Leonard Bernstein said: «This is the best hall in which I directed in South America. After the concert I told the reporters that the sound is excellent on stage, and I would like to be able to take that part of the hall to New York». Over the stage there is a folded wooden ceiling that complements the acoustic project of the Bolt, Beranek & Newman firm. The hall is considered one of the five best in the world, a versatile auditorium, used for concerts, theater, cinema and meetings, although its most moving use is for graduation ceremonies.