The Last Supper
More information about Leonardo da Vinci's fresco 'The Last Supper' can be found here and here.

Leonardo da Vinci took his time when he painted The Last Supper. Completion of the painting took more than three years. Leonardo made several studies. On the sketch below you can see Leonardo Da Vinci puzzled a lot with the composition of the twelve disciples. On the actual painting they are placed in four groups of three persons.