JSU Militants at the Fernán Núñez Palace's Façade. The Palace of Fernán Núñez is a unique building located in Calle Santa Isabel in Madrid, Spain. It’s the headquarters of the Spanish Railways Foundation and one of the most magnificent residences of the 19th century in Madrid. The Palace was built by order of the 7th Count of Cervellón, II Duke Consort of Fernán Núñez.