This is best exemplified in the Siheyuan, which has consisted of an empty space surrounded by buildings connected with one another either directly or through verandas. "Sky well" (天井): Although large open courtyards are less commonly found in southern Chinese architecture, the concept of an "open space" surrounded by buildings, which is seen in northern courtyard complexes, can be seen in the southern building structure known as the "sky well". This structure is essentially a relatively enclosed courtyard formed from the intersections of closely spaced buildings and offer small opening to the sky through the roof space from the floor up.