It's hard to get a proper view of the trim façade of this 18th-century palazzo, hemmed in as it is by other buildings. One of the high points in Ferdinando Sanfelice's architectural career, it has a no-nonsense double stairway in cool grey volcanic stone, with a beautifully cut marble-pillared balustrade. The apartments feature fine frescoes and original furniture. The main entrance in Via Egiziaca was closed in 1799 by the Prince of Cassano in mourning for the death of his son Gennaro, one of the leaders of the short-lived Parthenopean Republic. Gennaro was beheaded in Piazza del Plebiscito, and the entrance, which at the time enjoyed an unobstructed view of the Royal Palace, remained closed until bicentenary celebrations in 1999. The palazzo is now the headquarters of the Italian Institute for Philosophical Studies.