The Casa de la Moneda (Coining House) below the Alcázar is one of Segovia's most overlooked monuments — a 16th-century royal mint built by Philip II that was the first mechanised factory in Spain. The building sits on the banks of the Eresma river, which powered its hydraulic coin-stamping hammers. It produced standardised gold and silver currency for the Spanish Empire at scale, and it operated continuously for over two centuries.
The building is monumental and austere, designed by Juan de Herrera, the architect of El Escorial. The museum inside explains the minting process and the history of Spanish coinage, but the building itself is the main event. Combined with the walk along the river valley to the Monastery of El Parral, this is one of the best off-the-beaten-path excursions in Segovia.