Die Kreuzigung des Heiligen Petrus und die Enthauptung Johannes des Täufers

This strip of wood is barely a hand high. It ran along the base of a large altarpiece Masaccio painted in 1426 for a private chapel in a Pisa church, and it packs two executions into a single panel. Saint Peter is crucified head downward, at his own request, so as not to imitate the death of Christ, and beside him Saint John the Baptist is beheaded. Masaccio was about 25 and would be dead within two years, yet even at this tiny scale he gives the figures real weight and stands them in space you can believe in, the quality that sent younger Florentine painters to study him. The altarpiece was later taken apart and its pieces scattered, which is how this base panel came to Berlin while its Madonna ended up in London.