Lagoa das Furnas is located in the crater of a dormant volcano with a maximum length of 2025 m, maximum width of 1600 m, maximum depth of 12 m and occupies an area of ​​1.90 Km2 and is 281 m above sea level . It is one of the four largest lagoon water bodies in the Azores. The territory of the Lagoa das Furnas watershed constitutes a significant part of the Protected Landscape Area within the Natural Park of the Island of São Miguel. The lagoon is within the Furnas Volcanic Complex and has been classified as a Ramsar site since 2008, under the Convention on Wetlands, whose shores and shallow waters are among the best habitats for water birds migrating through the Azores.

Regarding the aquatic fauna, there are the following species in Lagoa das Furnas: Ruivo (Rutillus rutillus); Carp (Cyprinus carpio); Lucius (Esox lucius); Perch (Perca fluviatilis) and Sandre (Sander lucioperca).

The shores of Lagoa das Furnas have a great wealth of bryophytes, highlighting the species of leafy liverworts (Radula nudicaulis, Aphanolejeunea sintenisii and Telaranea europaea), the acrocarpic moss (Alophosia azorica), among others.

The area surrounding Lagoa das Furnas is also characterized by a high richness in invertebrate species such as mollusks and insects, with around 50 species of mollusks having been recorded, of which 19 are endemic and about 12 are endemic species of insects.

On the south bank of the lagoon, the Furnas Monitoring and Research Center (CMIF) was inaugurated, which aims to implement and disseminate ecological recovery actions for the quality of the water and the ecosystem of the Lagoa, within the scope of the programs and actions of the Land Management Plan of the Lagoa das Furnas Hydrographic Basin (POBHLF).

On the north bank of the lagoon is located the Caldeiras da Lagoa das Furnas where Cozido das Furnas is made.

On the north bank of the lagoon, the Caldeiras da Lagoa das Furnas and the Parque da Grená.

There is also a circular trail from Lagoa das Furnas with an easy walking difficulty, approximately 3 hours long. This pedestrian route begins and ends in the center of the parish of Furnas.