2000 years old, worth £1.8 million, banned from the USA, not publicly exhibited until 1999.
Meet history’s most expensive piece of gay porn: The Warren Cup

One side depicts a man (the active participant or erastes) engaging in anal sex with a young man (the catamite, eromenos, or passive participant), who lowers himself onto the erastes using a rope or support from the ceiling in roughly the modern sexual position of reverse cowgirl. Meanwhile a boy, perhaps a slave, watches surreptitiously from behind a door — the inferior status of a slave in Roman eyes would make him suitable to this role of voyeur. The other side depicts two young men making love. Both scenes also include draped textiles in the background, as well as a kithara (lyre) in the former scene and auloi (pipes) in the latter. These, along with the careful delineation of ages and status and the wreaths worn by the youths, all suggest a cultured, elite, Hellenized setting with music and entertainment.

Found in this essay about boy love, tweeted by fishfawn & posted on reddit