Aguilar de Campoo

Aguilar de Campoo has been occupied in turn by Cantabrians, Romans, Visigoths, and Moors — a few village names like Cordovilla and Zalima are the main traces of the Arab period. The town's medieval importance grew sharply in 1255, when Alfonso X signed the first Royal Charter of Castile here, a document now held by the Hispanic Society of America. The town held that royal privilege until 1332, after which it became the seat of one of Castile's largest administrative districts, the Merindad de Aguilar de Campoo, covering 262 settlements across what are now Palencia, Cantabria and Burgos.

Noble families shaped the following centuries. The Infante Tello de Castilla held the lordship from 1339 until his death in 1370 and became the founding ancestor of the Marquises of Aguilar. The Catholic Monarchs created the Marquisate in 1480, and in 1520 it was elevated to the rank of Grandee of Spain. King Charles I stayed at the Marquises' Palace in October 1517 on his first visit to Spain, and again in July 1522 on his return from Germany. One of the thirty survivors of Magellan's first circumnavigation of the globe, completed in September 1522, was Juan Martín, a native of Aguilar de Campoo.

Aguilar de Campoo was declared a protected historic-artistic ensemble in 1966. Its monuments span Romanesque, Gothic and Renaissance styles.

The Monastery of Santa María la Real, a former Premonstratensian abbey, now houses the Foundation of the same name, a Centre for Romanesque Studies, and a Museum of the Territory and Romanesque Art. The Collegiate Church of San Miguel and the Church of Santa Cecilia — a national monument — are among the main religious buildings, as is the Monastery of Santa Clara, also a national monument.

Six of the town's original seven medieval gates survive: the Puerta de Reinosa (which retains a Hebrew gravestone), the Puerta de la Tobalina, the Barbacana or Paseo Real gate, the Puerta del Portazgo, the Puerta de la Cascajera, and the Puerta de San Roque. The medieval castle and stretches of town wall also remain.

Around the Plaza Mayor stand several palaces, including the baroque Palace of the Marquises of Aguilar — one wing survives — and the Palace of the Fontaneda, along with manor houses built in the Cantabrian style, with wide south-facing galleries. The Pisuerga river is crossed by several bridges of medieval origin, including the Puente Mayor and the Puente del Portazgo. The surrounding landscape of Las Loras was designated a UNESCO Global Geopark in 2017, the first in Castile and León.