Popularly attributed to Vignola (architect of the Palazzo Farnese in nearby Caprarola, in reality it was also commissioned by Cardinal Alessandro Farnese, who also built the Palazzo Farnese), but to the architect Antonio Gentili from Faenza.
Built in sandstone, it features three unicorns (often called "seahorses") from whose mouths water flows to fill the two basins below. (c) it.wikipedia.org/wiki/Ronciglione