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 lead 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 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 (cubiculi) and (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