Castle of Grajal de Campos Monument · Grajal de Campos, Esla-Campos, León Considered the first artillery castle in Spain, it was built between 1517 and 1521 by order of Hernando de Vega to designs by Lorenzo de Aldonza. It has a quadrangular plan with four towers for the cannon and has been a Monumento Nacional (Spain's heritage designation in force until 1931) since 1931. Photo: David Daguerro (CC BY-SA 3.0) What to see and do in Grajal de Campos