For 10 points, Piero della Francesca's cycle about what object depicts its discovery by Saint Helena?
African boatmen and Armenian merchants appear in a painting by Carpaccio in which this object heals a madman. The last Queen of Cyprus, Caterina Cornaro, prays in a crowd on the left side of a canvas in which Andrea Vendramin emerges from the water under a bridge holding this object. White-robed men parade this object in a golden box in Gentile Bellini's Procession in St. Mark's Square, one of the paintings about this object commissioned for the Grand Hall of a Venetian confraternity. This object sits next to a canopied throne on the right of a painting featuring colorful banners over a chaotic battle scene. At the top left of a nocturnal painting, an angel descends to show this object to a (*) sleeping king in a tent. This object appears in the frescos The Meeting of Solomon and the Queen of Sheba, Battle of Heraclius and Chosroes, and Constantine's Dream. For 10 points, Piero della Francesca's cycle about what object depicts its discovery by Saint Helena?
African boatmen and Armenian merchants appear in a painting by Carpaccio in which this object heals a madman.
the True Cross [or the Holy Cross; or anything indicating a relic of fragment of the cross]