Madrid's Malasana, Chueca, and La Latina neighborhoods offer great bases with authentic character. Barcelona's Eixample district is central and well-connected; El Born and the Gothic Quarter suit those who want to walk everywhere.
Seville and Granada are compact and walkable — staying near the cathedral in Seville or the Realejo district in Granada puts you in ideal positions. Paradores (state-owned heritage hotels in castles and monasteries) are a uniquely Spanish accommodation experience.