British Museum — London, England, United Kingdom

This is one of three engravings from the same few years that historians consider his best — what it actually means has apparently been argued over for centuries.

This was originally made to open one of his illustrated prophecy books, not meant to hang on its own. From what I can find, he loved this particular design enough to keep redrawing it for the rest of his life - one copy was finished only weeks before he died.

It's a print rather than a painting — one of thirty-six goes at the same mountain, run off the blocks in the thousands and sold cheap, more or less a poster. The blue doing all the heavy lifting was a newish imported pigment then, according to Wikipedia, which is part of why it looks the way it does.

Nobody has ever agreed on what this is about, which hasn't stopped four hundred years of people having a go. The grid on the wall is a magic square — every row and column adds up to the same number, and the date's worked into the bottom row. It was apparently printed around the same time as two others that get treated as a matching set.

Prints like this come in states: you print a few, then go back and cut into the metal plate again, so the same picture exists in versions that don't match each other. Supposedly he gouged out whole sections of this one between printings and redrew them, and the later version came out far darker than the first.