Bird's nest soup

Edible bird's nests, also known as swallow nests , are bird nests created from solidified saliva by edible-nest swiftlets, Indian swiftlets and other swiftlets of the genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia, which are harvested for human consumption. Swallow nests have been used as a delicacy for over 400 years, most often as soup. They are particularly prized in Chinese cuisine due to the rarity, high protein content and rich flavor, and are among the most expensive animal products consumed by humans, with prices up to about $4,300 per pound ($9,500/kg) depending on grading. The type or grading of a swallow nest depends on the bird species, as well as the shape and color of the bird's nest. It is usually white in color, but there also exists a red version that is sometimes called 'blood nest' (血燕). According to traditional Chinese medicine, it promotes good health, especially for the skin.

Source: Wikipedia