Represa Billings is the largest reservoir in the metropolitan region of São Paulo, covering 127 km² with a total volume of approximately 1,228.7 million cubic meters. The reservoir has a mean depth of 10 meters and a perimeter of roughly 900 kilometers, giving it an extensive and irregular shoreline. It spans portions of several municipalities including São Paulo, Santo André, São Bernardo do Campo, Diadema, Ribeirão Pires, and Rio Grande da Serra. The reservoir is divided into two compartments separated by a barrier: the larger Pedreira section at 112 km² and the smaller Rio Grande section at 15 km². Average water residence time ranges between 50 and 100 days.

Kayaking is a popular activity on the reservoir. A notable paddling destination is the area around Ilha do Bororé, a neighborhood in the southern zone of São Paulo in the Grajaú district, which is accessible by boat and offers an ecotourism experience distinct from the urban surroundings. Organized boat tours operate along a route connecting the dam area to Ilha do Bororé, and this corridor works well as a paddling route.

The primary access routes to the reservoir are via Avenida dos Bandeirantes and Rodovia dos Imigrantes, and having a car is strongly recommended, as public transportation requires multiple bus transfers and significant walking. Access points vary around the reservoir's extensive perimeter, and paddlers should research the specific area they intend to visit in advance.

Water quality is a notable concern. The reservoir has documented problems with wastewater discharge and floating garbage including plastic bottles, and there are issues associated with unapproved human settlements in surrounding areas. Fishing is permitted in authorized areas, with some restrictions tied to water quality. Common fish species include trahira, giant trahira, and redbreast tilapia. Sun protection is advisable given the open water exposure, particularly during warmer months.

The reservoir was originally constructed for hydropower generation, with construction beginning in 1925 and reaching maximum capacity in 1950. It is named after Asa White Kenney Billings, the American hydroelectric engineer who oversaw its development. Today it also serves as a water supply source for approximately 1.8 million people.