Castle of Alaejos

The Castle of Alaejos survives today as a largely underground ruin in the small town of Alaejos, in the province of Valladolid, Castile and León. Little rises above ground level, yet the site carries a history that shaped the course of Castile, and it has recently been opened to the public as a walkable archaeological site.

Who built the castle, and when?

The fortress was commissioned around 1453 by Alonso de Fonseca y Ulloa, bishop of Ávila and later archbishop of Seville. Like many strongholds raised by powerful clerical families in 15th-century Castile, it combined the roles of noble residence, prison, and control point over the surrounding lands held by the Fonseca family.

What can you actually see on site?

Most of what remains sits below the modern ground level: the moat that once ringed the fortress, underground passages linking different parts of the complex, and wells — both for water and for storing snow and ice, a common feature of Castilian castles of the period. The original structure had four corner towers plus a keep (torre del homenaje), the defensive core of any medieval Castilian fortress. Today the remains are marked out and prepared for visits as part of organized guided tours.

What actually happened here?

The castle's fame rests chiefly on an episode from 1467 known as "El Desliz de Alaejos" — roughly, "the Alaejos slip." Queen Joan of Portugal, wife of King Henry IV of Castile, was held here under the custody of Archbishop Alonso de Fonseca. During her stay, the queen had an affair with Pedro de Fonseca y Ulloa, the archbishop's nephew, which resulted in the birth of twins. The scandal cast doubt on the legitimacy of the queen's daughter, the infanta Joan known as "la Beltraneja," weakening her claim to the Castilian throne in favor of her aunt, the future Isabella the Catholic — a scandal that fed directly into the war of succession that followed.

The second defining moment came in 1520, during the Revolt of the Comuneros (Guerra de las Comunidades de Castilla). The comuneros, hostile to the Fonseca family, attacked and largely destroyed the fortress — an episode regarded as one of the movement's earliest setbacks in the conflict. The castle was later rebuilt in part, but it never regained its former standing and gradually fell into ruin.

How do you get there, and when's the best time to visit?

Alaejos sits in the province of Valladolid, close to Medina del Campo, in Castile and León — the easiest approach is by car from Valladolid or Salamanca. The archaeological site is open through free guided tours organized by the local town council, and visits require a phone reservation with the Alaejos tourist office in advance. Groups need a minimum of 6 and a maximum of 20 people, so booking ahead is worthwhile. From October to March, tours run on Fridays from 16:00 to 18:30, and on Saturdays and Sundays from 10:00 to 13:30 and from 17:00 to 19:30.

Frequently asked questions

Is entry to the castle free? Yes — the guided tours are free of charge, but a phone reservation is required beforehand.

Can you visit on your own, without a guide? No. Visits are run exclusively as groups organized by the town council, so it's worth calling ahead to arrange a time.

Why is the castle in ruins? The fortress was heavily damaged during the Comuneros' siege in 1520 and, despite later rebuilding attempts, never recovered its former importance.

What's the most notable episode in the castle's history? The 1467 affair involving Queen Joan of Portugal, held prisoner here, which had a direct bearing on the struggle over the Castilian crown.