The fortifications at Castelmur may be, after the Three Castles of Bellinzona, the most important example of medieval valley fortifications in modern Switzerland.
The castle site has been occupied and fortified since at least the Roman era. The important trade road over the Septimer Pass runs through the Val Bregaglia. The Romans built a guard station and village named 'Murus' according to the 3rd century Itinerarium Antonini. The foundations of several buildings as well as one building's hypocaust and two small votive altars have been excavated from the Roman settlement.
After the fall of the Western Roman Empire the Castelmur next appears in 842 as castellum ad Bergalliam. At that time it was owned by the Emperor and held by Constantius of Sargans. In 960 Emperor Otto I granted the castle and right to collect tolls to the Bishop of Chur to help secure this important alpine trade route. In 988 Emperor Otto IIIconfirmed his grandfather's grant to the Bishop and specifically mentioned both the castle and the nearby Nossa Donna Church. The current tower was probably built around 1200.
Over the following centuries the Bishop of Chur and the town of Chiavenna quarreled over Castelmur and in 1121 or 1122 the town captured the castle. However, Pope Callixtus II intervened and forced Chiavenna to return the castle to Chur. In 1190 the Bishop granted the castle to Albertus de Castello Muro or Castelmur. His descendants ruled over the castle until 1264 when Albertus Popus Castelmur stole cattle from the nobles of Chiavenna and Piuro, led to an invasion and the castle being conquered in 1268. These nobles held the Castelmur for four years before returning it to the Castelmurs in 1272. Around 1340 the Bishop reclaimed the castle and then mortgaged it to the Planta family for 200 Marks. To discourage the Planta family from trying to completely annex the lucrative castle and tolls, in 1410 the Bishop mortgaged it to Jacob Perutt von Castelmur for 150 Gulden. Twenty years later the Bishop used a loan from the Salis family to buy out the mortgage and give it to them. In 1490, for the last time, the Bishop gave the castle to Michel Pfannholz. However, he abandoned it in 1538 and left the castle to fall into ruin.
The castle ruins were repaired and cleaned in the 19th century by Baron Giovanni de Castelmur. In addition to the castle, he repaired and rededicated the nearby church of S. Maria (Nossa Donna). The church's bell tower is a Romanesque construction, but much of the church itself, including the nave are from this 19th century renovation. The church was first mentioned in 988.
The original fortification was a wall or letzi that straddled the valley between the Maira river and the castle hill. This wall, which was up to 3.7 meters thick, had a gate that could be blocked by logs if needed. The remains of this wall are north-west of the main tower. In the 12th century a square tower with a ring wall were built on top of the steep outcrop. This tower allowed a noble family to take up residence and changed Castelmur from a toll collecting station into a regional administrative center. The five story square tower was 12 m on a side with 2.4 m walls on the lowest story. Much of this tower is still visible. The castle church was built below the castle hill south of the main tower. At some point, a second tower was added on a tall hill south of the main tower. This building measured about 10 m × 10 m, though very little of it still remain.References:
The Palazzo Colonna is a palatial block of buildings built in part over ruins of an old Roman Serapeum, and has belonged to the prestigious Colonna family for over twenty generations.
The first part of the palace dates from the 13th century, and tradition holds that the building hosted Dante in his visit to Rome. The first documentary mention notes that the property hosted Cardinal Giovanni and Giacomo Colonna in the 13th century. It was also home to Cardinal Oddone Colonna before he ascended to the papacy as Martin V (1417–1431).
With his passing, the palace was sacked during feuds, and the main property passed into the hands of the Della Rovere family. It returned to the Colonna family when Marcantonio I Colonna married Lucrezia Gara Franciotti Della Rovere, the niece of pope Julius II. The Colonna"s alliance to the Habsburg power, likely protected the palace from looting during the Sack of Rome (1527).
Starting with Filippo Colonna (1578–1639) many changes have refurbished and create a unitary complex around a central garden. Architects including Girolamo Rainaldi and Paolo Marucelli labored on specific projects. Only in the 17th and 18th centuries were the main facades completed. Much of this design was completed by Antonio del Grande (including the grand gallery), and Girolamo Fontana (decoration of gallery). In the 18th century, the long low facade designed by Nicola Michetti with later additions by Paolo Posi with taller corner blocks (facing Piazza Apostoli) was constructed recalls earlier structures resembling a fortification.
The main gallery (completed 1703) and the masterful Colonna art collection was acquired after 1650 by both the cardinal Girolamo I Colonna and his nephew the Connestabile Lorenzo Onofrio Colonna and includes works by Lorenzo Monaco, Domenico Ghirlandaio, Palma the Elder, Salviati, Bronzino, Tintoretto, Pietro da Cortona, Annibale Carracci (painting of The Beaneater), Guercino, Francesco Albani, Muziano and Guido Reni. Ceiling frescoes by Filippo Gherardi, Giovanni Coli, Sebastiano Ricci, and Giuseppe Bartolomeo Chiari celebrate the role of Marcantonio II Colonna in the battle of Lepanto (1571). The gallery is open to the public on Saturday mornings.
The older wing of the complex known as the Princess Isabelle"s apartments, but once housing Martin V"s library and palace, contains frescoes by Pinturicchio, Antonio Tempesta, Crescenzio Onofri, Giacinto Gimignani, and Carlo Cesi. It contains a collection of landscapes and genre scenes by painters like Gaspard Dughet, Caspar Van Wittel (Vanvitelli), and Jan Brueghel the Elder.
Along with the possessions of the Doria-Pamphilij and Pallavacini-Rospigliosi families, this is one of the largest private art collections in Rome.