The Tomb of Caecilia Metella and its Roman concrete

The Tomb of Caecilia Metella is a mausoleum located just outside Rome at the three mile marker of the Via Appia. It was built during the 1st century BC to honor Caecilia Metella, the daughter of Quintus Caecilius Metellus Creticus, a consul in 69 BC, and the wife of Marcus Licinius Crassus. The monument was probably built by her son, also named Marcus Licinius Crassus. It is one of the most well-known and well-preserved monuments along the Via Appia and is a popular tourist site. In 2013, it was part of a museum circuit that was the twenty-second most visited site in Italy, attracting 245,613 visitors.

The monument consists of a cylindrical drum, or rotunda, atop a square podium, with the Caetani Castle attached at the rear. The square podium stands at 8.3 meters tall, and the cylindrical drum stands at 12 meters. The foundation of the tomb rests partially on tuff rock and partially on lava rock, which is part of an ancient lava flow from the Alban Hills from 260,000 years ago. The core of the podium was cast in several layers of concrete, ranging from 0.7 to 0.85 meters thick. Travertine facing-blocks were used as a frame to help the concrete layers form. The rotunda was built in a similar fashion, using travertine blocks on the outermost section with cement poured in the middle. The walls of the circular tower are 24 feet thick, while the adjoining Caetani Castle was made of a thin wall of tufa.

The interior of the tomb is divided into four sections: the cella, the upper and lower corridors, and the west compartment. The cella is a tall, circular shaft rising through the center of both the podium and the rotunda and was used for funerary purposes. The shaft is about 6.6 meters in diameter at the bottom and tapers to 5.6 meters at the top. An oculus at the top allows light to enter. Throughout the cella, there are over 143 cut outs, divided into 12 rows, which were used as putlog holes during the construction of the monument. The upper corridors are believed to be the main entrance to the cella.

The tomb was originally topped with a cone-shaped earthen mound, but this has been replaced by medieval battlements. The Caetani family bought the estate in 1302-1303 and built a fortified camp, or castrum, next to the tomb, which included stables, houses, warehouses, the church of St. Nicholas, and a palace. This construction replaced a preceding 11th-century building. The Caetani used this fort to control road traffic and collect tolls. The property was later passed to the Savelli and the Orsini before becoming property of the Roman Senate. The monument was abandoned in 1485, but it was saved during the Renaissance and Romantic periods because the two structures protected one another from destruction.

The Tomb of Caecilia Metella remains a notable example of Roman architecture. Its construction, utilizing layered concrete and stone, showcases the engineering of the 1st century BC. As a landmark on the Via Appia, it continues to be a site of significant historical and architectural interest.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons