Claudi Alsina (Barcelona, 1952) is Head of Mathematics at the Architecture Department of the University of Barcelona. He has worked widely in mathematical research and also innovation and promotion of education. Author of numerous popular mathematics books, he is a renowned writer and conference speaker. This guide is the result of his many travels and his particular way of looking at the world. At Ariel he has also published Vitaminas matemáticas and El club de la hipotenusa.