A twenty-thousand-year-old Bajoran icon painting, returned by the Cardassians in 2373, whose depiction of an obelisk gives Benjamin Sisko the clue to finding the lost city of B'hala.
The painting appears in the fifth-season Deep Space Nine episode Rapture. It is the only known image of B'hala, a sacred city lost for twenty thousand years, and had been taken from Bajor during the occupation before the Cardassians gave it back.
Sisko becomes fascinated by an obelisk in the picture, which marked the city's position in the heavens but shows only two of its faces. Noticing its reflection in the painted water, he recreates the monument in a holosuite to work out the hidden symbols, and is struck by a plasma discharge from the console.
The accident leaves him with visions of startling clarity. He finds the buried city within days, and goes on to warn Bajor against joining the Federation at once, a prophecy that keeps the planet out of the Dominion's first assault.