The Prado itself is sharing credit with the Reina Sofia Museum in Madrid for the city 's main summer show '' Picasso : Tradition and Avant-Garde , '' which celebrates both the 125th anniversary of Picasso 's birth and the 25th anniversary of the return to Spain of his landmark painting , '' Guernica , '' which hung in '' exile '' at the Museum of Modern Art in New York during the Franco dictatorship .