If you are an European art aficionado, you're spoilt for choice in Madrid between the famous triangle formed by Reina Sofia, The Pardo and the Thyssein...
But if you are pressed for time, and, have to pick one, my choice would be the Renia Sofia, only for the Guernica.
Guernica is a painting by Pablo Picasso, depicting the Nazi German bombing of Guernica Spain, by twenty-eight bombers, on April 26, 1937 during the Spanish Civil War. The attack killed between 250 and 1,600 people, and many more were injured.
The Spanish government commissioned Pablo Picasso to paint a large mural for the Spanish display at the Paris International Exposition in 1937.
The Guernica bombing inspired Picasso. Within 15 days of the attack, Pablo Picasso began painting this mural. On completion Guernica was displayed around the world in a brief tour, becoming famous and widely acclaimed. This tour brought the Spanish civil war to the world's attention. Guernica epitomizes the tragedies of war and the suffering war inflicts upon individuals.
At approx 25 ft x 11 ft, the Guernica occupies an entire wall and is fascinating, awe-inspiring and repulsive in its depiction of a scene of death, violence, brutality, suffering, and helplessness.
Done in black, white and shades of grey, its said that Picaaso chose the colour scheme to convey the chronological nearness of a newspaper photograph and the lifelessness war affords.
For a symbol of the destruction that a war can wreak, the good thing is that a lot of people recognize the painting. They may not know that it's a Picasso, but they recognize the image. In that sense, its an icon for the ravages that war can bring, and an absolute must see...