Palace of Gastañaga, Gothic palace in central Llanes, Spain.

The Palace of Gastañaga is a Gothic structure in central Llanes consisting of two independent buildings connected by elevated passages. The stone walls display characteristic medieval features including pointed arches and paired window openings.

The building originated in the 14th century with Gothic characteristics. In 1656 it underwent major reconstruction while deliberately preserving its original medieval formal elements.

The palace is also called San Nicolás or de los Rivero, after the family that rebuilt it in 1656 under Juan de Rivero y Posada, regidor of Llanes. The carved sandstone coat of arms on the noble floor still marks that lineage; the building closed the gap beside the vanished San Nicolás gate, where the walled town met the fishermen's quarter.

The palace occupies the Calle Mayor at the point where the walled town opened toward the fishermen's quarter through the vanished San Nicolás gate, of which the building was the defensive bastion. Visitors approach on foot along this street; the sandstone coat of arms and the second-floor exit onto the old patrol walk are visible from the pavement.

The building functioned as both a noble residence and a defensive fortification with specialized defensive walkways. This combination of living space and protective function was typical for wealthy families in the medieval town.