The Bloodstained House of Coenraad van Beuningen (1622-1693) (Amstel 216. Trams 9, 14 & 20 and all three Metro trains, to Waterlooplein. Cross the Amstel, turn left and cross the Herengracht.)
The house is an imposing, though somewhat dull building on the Amstel. Along the front, at eye level, are faint scribbles in what looks like reddish-brown chalk. They don't look exactly like the other scribbles on the wall. They're much older.

Until I take my own photos, look at these.

Coenraad van Beuningen was a brilliant member of Amsterdam's regent class (similar to the French intendant class or the old political families of the U.S.) and was mayor of Amsterdam and a master diplomat. His political peak came in 1672, when King Louis XIV tried to claim the lowlands because his queen was Spanish (the Netherlands had won their independence from Spain a hundred years ago). Louis' army had taken nearby Utrecht and Naarden and Amsterdam was in confusion. Van Beuningen managed to forge an alliance that included England to repel the French.

Van Beuningen went into a decline after this. The Prince of Orange, nominal ruler of the lowlands, wanted to use the new alliance to invade France. Van Beuningen demurred, on the grounds that the alliance wouldn't survive the venture. He was right, but he suffered politically and, as it turned out, mentally. A few years later, he speculated wildly in East India Company shares and bankrupted himself. Within this time, he married his mistress of some years. He had been celibate up until this time. It's not known whether he was afterward. Either way, the marriage was a bad one.

In 1689 he went cabalistic. A follower of the German mystic Jakob Boehme, he pestered local theologians with his theories on the nature of the Godhead and generally ranted like a street person. He also had apocalyptic visions, seeing red fireballs and a rainbow-colored coffin floating above the city. Around this time, legend has it that he slashed his arms with a scalpel and scrawled messages in his own blood on the outside wall of his house. Chalk or paint is more likely, but the writings have resisted 300 years of cleanup attempts, including a 1930s effort using acid and high-pressure hoses. One can see a sailing ship, two attempts to write "van Beuningen" and one instance of "Jacoba," the name of his wife. There are also Hebrew letters, but they're difficult to discern.

After years of mental and physical suffering that he likened to the sufferings of Christ, van Beuningen died, on 26 October, in poverty. Among his effects, valued at less than f 100, was an oval mirror. No one knows what he saw in it, and nobody knows where it is now

Sources:
I.H. van Eeghen, De Huizen van Coenraad van Beuningen, Tijdschrift Genootschap Amstelodamum, Jaargang 58 (1971), pp98-108.
Geert Mak, Amsterdam: A Brief Life of the City. Harvill Press (1999, London).
M. Sluyser & Fred. Thomas. Twaalf Burgemeisters: Vofj Hondred Jaar Amsterdam. Andries Blitz (1939, Amsterdam).