The “solid gold cube” crypto promo that surfaced in New York this week has turned out to be hollow on the inside, with onlookers online lampooning the stunt as an appropriate critique of the extravagant promises of crypto and blockchain tech.

On Wednesday, Artnet reported that a 24-carat 410-pound gold cube worth $11.7 million had been placed in Central Park surrounded by a “heavy security detail” as part of a promo for German artist Niclas Castello’s crypto project dubbed Castello Coin (CAST).