Popularly known as the Casa del Cordón, the palace of the Constables of Castile is a 15th-century palace that stands in the historic centre of Burgos, presiding over the old Plaza del Mercado Mayor, which was formed by the current Plaza de La Libertad and Plaza Santo Domingo de Guzmán. Its promoters were Pedro Fernández de Velasco, Constable of Castile, and the Countess Mencía de Mendoza y Figueroa, his wife.

The initial design is attributable to Juan de Colonia and his son Simón and it is a civil building in the Gothic style of great beauty and harmony, although today it has been greatly modified with respect to the original design. Throughout the building there are numerous representations of the heraldic coats of arms of the couple who owned the palace (Velasco and Mendoza), and in particular the two coats of arms above the main door are linked by means of a Franciscan cord, also sculpted in the stone. A cord or chains hung on the door of a house indicate that a king has slept there. Doña Mencía was a devotee of San Francisco and had the Franciscan cord sculpted. This cord is the one that, in popular lore, gave the building its name. It currently houses a cultural centre and the headquarters and head offices of a bank.

When Pedro Fernández de Velasco was appointed Constable of Castile in 1473, his residence in Calle Cantarranas (now Calle de San Lorenzo) proved to be inappropriate for such a high public office. For this reason, in 1476, work quickly began on the construction of the new palace in which the highest political authority of the kingdom would reside after the monarch himself. The site chosen was the Plaza del Mercado Mayor, formerly known as the Corral de las Vacas, and there are indications that an earlier building was used as a base, probably the so-called palace of the Princess. The person in charge of the works was Juan de Colonia, who undertook them in collaboration with his son Simón, who was to complete the construction.

The original layout was a palace of notable dimensions, with a central courtyard with double Gothic arches similar to those found in monastic cloisters. The main entrance was located on the south façade, with gardens attached to the east façade. This area is the one with the oldest remains, with Gothic capitals from the 14th century, probably from the previous building.

The main façade had two towers and a doorway with a Franciscan cord carved in the stone and which serves as a link to the coats of arms of the Velasco and Mendoza-Figueroa families, as well as the monogram IHS surrounded by the Eucharistic sun.

In the second phase of construction, between 1484 and 1497, the central courtyard was defined. It is an arcaded courtyard, in imitation of religious cloisters, with two storeys, to which the rooms open, serving as a distribution of space. Each side of the courtyard has five arches per floor, with a small frieze that also serves as a railing, on which we again find the heraldic coats of arms of the owners of the house. This constant representation of the arms of his wife, Mencía de Mendoza y Figueroa, gives an idea of how important it was for the Constable to have been related to one of the most powerful families in Castile.

The west façade probably had a very similar layout to the south façade, although it was completely lost (as was the north façade) and what we see today are reconstructions from the 20th century.

The building is made of limestone from the Hontoria quarries.