Five centuries before anyone used the word "psychedelic", a Dutch painter made this. Open the triptych's wings and you get three panels: on the left, Eden; in the middle, a vast garden crowded with naked people, giant fruit, birds the size of houses and impossible pink architecture; on the right, a nightmare Hell of knives, instruments of torture and a man-tree with a tavern in his body.

Nobody agrees exactly what it means. Is the middle panel a warning about pleasure, a vision of paradise lost, or something weirder? Bosch left no explanation, and that is a large part of the fun.

Hell is full of musical instruments used as torture devices — a harp with a body strung on it, a lute pinning a sinner. And on one damned soul's backside there is a written line of music. In 2014 a student transcribed it and recorded it; the "butt song" became an internet sensation. It is, honestly, not bad.

Spend ten minutes zooming into any corner and you will find something you have never seen in any other painting.