Sasso Corbaro, known as Unterwalden Castle after 1506 and Saint Barbara's Castle after 1818, is about 600 m south-east of town on a rocky hill. Unlike the other two castles Sasso Corbaro is not integrated into the city walls. The first part of the castle was the north-eastern tower which was built in 1478 to close a gap in the defenses of the city. In 1479 a small garrison was moved to the tower. During peacetime the tower was used as a prison, though at least one prisoner escaped in 1494. The walls and south-west tower were added later. The castle was struck by lightning multiple times during the 16th and 17th centuries, and by 1900 was falling into ruins.
The fortress is a 25 by 25 m square with square towers on the north-east and south-west corners. The east wall is 1.8 m thick and other walls are about 1m thick. All the walls have machicolations and swallowtail merlons for defense. The entrance to the courtyard is through the western wall, and contains evidence of a portcullis. The two story buildings on the south and west walls were both living quarters with a gabled roof. The castle chapel is located on the eastern side of the courtyard.
The north-eastern keep currently has four stories, though no records exist of its original height and roof. It was used as a living area when the castle was occupied.
Today, Sasso Corbaro Castle houses the Sala Emma Poglia which is the 'wooden room' built for the Emma family during the 17th century. Originally located in the entrance hall of their home in Olivone in the Blenio Valley, the room was purchased by the Canton of Ticino in 1944 and housed first in Castelgrande before being moved to the Sasso Corbaro in 1989. The room is panelled entirely in walnut and also includes the stüva, stove which provided heating. The stove bears the crest of the Emma family (an eagle and a lion rampant). The museum also houses temporary exhibits. It is open from March until November.
References:The Basilica of Santa Maria in Trastevere is one of the oldest churches of Rome. The basic floor plan and wall structure of the church date back to the 340s, and much of the structure to 1140-43. The first sanctuary was built in 221 and 227 by Pope Callixtus I and later completed by Pope Julius I.
The inscription on the episcopal throne states that this is the first church in Rome dedicated to Mary, mother of Jesus, although some claim that privilege belongs to the Basilica di Santa Maria Maggiore. A Christian house-church was founded here about 220 by Pope Saint Callixtus I (217-222) on the site of the Taberna meritoria, a refuge for retired soldiers. The area was made available for Christian use by Emperor Alexander Severus when he settled a dispute between the Christians and tavern-keepers.
The church underwent two restorations in the fifth and eighth centuries and in 1140-43 it was re-erected on its old foundations under Pope Innocent II.