Cavaedium information

The well-preserved Tuscan atrium in the House of Menander, Pompeii. Note lararium in far corner by the stairs. Inwards-sloping roof supported by clear-span beams. View is through the tablinum, towards the front door.

The larger tetrastyle atrium of the Villa San Marco, Stabiae; four pillars support the roof. The central niche is the lararium; the two blocks of limestone (behind the pillar with the near-intact stucco) supported the arca, a strongbox or safe.^[1]

Cavaedium or atrium are Latin names for the principal room of an ancient Roman house, which usually had a central opening in the roof (compluvium) and a rainwater pool (impluvium) beneath it. The cavaedium passively collected, filtered, stored, and cooled rainwater. It also daylit, passively cooled and passively ventilated the house.

The atrium was the most important room of the ancient Roman house. The main entrance led into it; patrones received their clientes there, and marriages, funerals, and other ceremonies were conducted there. In earlier and more modest homes, the atrium was the common room used for most household activities; in richer homes, it became mainly a reception room, with private life moving deeper into the (larger) house. The atrium was generally the most elaborate room, with the finest finishings, wall paintings, and furnishings.

The atrium was entered either through a shop^[2] or by a straight, narrow passage from the street. The smaller, open room behind the atrium was the tablinum, usually the study of the master of the house. Behind it was a garden; temperature differences between the atrium and the garden drove a draft through the tablinum, making it the coolest room in the house. Unless curtains or movable partitions of the tablinum were closed, a visitor in the passage could see through the atrium and tablinum into the garden; care was taken to make this view impressive. Ideally, rooms off the atrium were arranged symmetrically, or at least to give the impression of symmetry. Bedrooms (cubiculum) and alae (the "wings" of the atrium, alcoves separated by a lintel but not a wall) typically opened off the sides of the atrium.

Small rural Roman buildings did not need atria; they were lit by windows and drew water from wells or watercourses. An urban house (domus), on the other hand, had to be built on a small, narrow lot, as urban land was expensive and street frontage was even more expensive. Theft was also a concern. Urban houses thus came to look inwards onto cortiles, enclosed courts, and light and water were brought in from above. Sometimes urban houses retained a walled garden at the rear, which later often became a peristyle, a sort of cloister surrounded by rooms. Large rural properties were sometimes built around large enclosed farmyards, but the Roman villa or country seat mimicked the city residence from which the wealthy owner generally came, and often had an atrium (or several). In later Roman history the atrium was sometimes also replaced by a peristyle, and rain-gathering with piped water from an aqueduct. The urban houses of poorer Romans might lack atriums entirely; but from (mainly Pompeiian) survey data, atriums, peristyles, or both are found in almost all Roman homes over 350 square meters in size, most over 170 square meters, and some over 50 square meters.^[3]

An older-style Roman domus, with a no-pillar Tuscan atrium and no more than a garden behind. Roughly 3rd century BCE.

A later Hellenized Roman domus. It has a Corinthian atrium, and the simple garden has been expanded into a room-ringed peristyle. Roughly 2nd century BCE.