El Castillo de Viñuelas, whose first references date back to 1285, is the most notable building on the hill. The current construction dates from the 18th century and has a square floor plan, with four large cylindrical crenellated towers at the corners.

The building is three storeys high, except for the towers, which are four storeys high. Its north face is the one with the greatest artistic and ornamental values: a central upper panel with a coat of arms, a continuous balcony on the first floor supported by columns that form a portico and two sentry boxes topped by spires. Inside, the Sala de Armas (Weapons Room) stands out.

Its attics are crowned by Gothic crests and gargoyles and its walls have niches with statuary and ornaments from the medieval temple of San Francisco, in the Segovian town of Cuéllar.

Inside the castle, which is now covered with ribbed ceilings and illuminated by chandeliers, there are rooms decorated with portraits of former heroes. French fireplaces of carved stone with heraldic coats of arms warm the halls, which have wainscots of brilliant tiles.