Guanabara Bay is 31 kilometers (19 mi) long and 28 kilometers (17 mi) wide at its maximum range. Its 1.5 kilometers (0.93 mi) wide mouth is flanked at the eastern tip by the Pico do Papagaio (Parrot's Peak) and the western tip by Pão de Açúcar (Sugarloaf Mountain).
The name Guanabara comes from the Tupi language, goanã-pará, from gwa "bay", plus nã "similar to" and ba'ra "sea." Traditionally, it is also translated as "the bosom of sea."
Guanabara Bay was first encountered by Europeans on January 1, 1502, when one of the Portuguese explorers Gaspar de Lemos and Gonçalo Coelho arrived on its shores. According to some historians, the name given by the exploration team to the bay was originally Ria de Janeiro "January Sound", then a confusion took place between the word ria, which at the time was used to designate a bay or a sound, and Rio "river". As a result the name of the bay was soon fixed as Rio de Janeiro. Later, the city was named after the bay. Natives of the Tamoio and Tupiniquim tribes inhabited the shores of the bay.
After the initial arrival of the Portuguese, no significant European settlements were established until French colonist and soldiers, under the Huguenot Admiral Nicolas Durand de Villegaignon invaded the region in 1555 to establish the France Antarctique. They stayed briefly on Lajes Island, then moved to Serigipe Island, near the shore, where they built Fort Coligny. After they were expelled by Portuguese military expeditions in 1563, the colonial government built fortifications in several points of Guanabara Bay, rendering it almost impregnable against a naval attack from the sea. They were the Santa Cruz, São João, Lajes and Villegaignon forts, forming a fearsome crossfire rectangle of big naval guns. Other islands were adapted by the Navy to host naval storehouses, hospitals, drydocks, oil reservoirs and the National Naval Academy.
There are more than 130 islands dotting the bay, including:
- Governador – site of Rio de Janeiro's Galeão - Antônio Carlos Jobim International Airport
- Ilha da Boa Viagem
The bay is crossed by the mighty President Costa e Silva Bridge, commonly known as the Rio-Niterói Bridge (13.29 kilometers (8.26 mi) long and with a central span 72 meters (236 ft) high) and there is heavy boat and ship traffic, including regular ferryboat lines. The Port of Rio de Janeiro, as well as the city's two airports, Galeão - Antônio Carlos Jobim International Airport (on Governador Island) and Santos Dumont Airport (on reclaimed land next to downtown Rio), are located on its shores. The Federal University of Rio de Janeiro main campus is located on the artificial Fundão Island. A maze of smaller bridges seamlessly interconnect the two largest islands, Fundão and Governador, to the mainland.In Guanabara Bay lies an Environmental Protection Area (APA), which is located mostly in the municipality of Guapimirim and given the name of (APA) Guapimirim.
Guanabara Bay's once rich and diversified ecosystem has suffered extensive damage in recent decades, particularly along its mangrove areas. The bay has been heavily impacted by urbanization, deforestation, and pollution of its waters with sewage, garbage, and oil spills.
There have been three major oil spills in Guanabara Bay. The most recent was in 2000 when a leaking underwater pipeline released 1,300,000 liters (340,000 US gal) of oil into the bay, destroying large swaths of the mangrove ecosystem. Recovery measures are currently being attempted, but more than a decade after the incident, the mangrove areas have not returned to life.
The bay is home to dozens of species botanical, zoological and ichthyological. Among the species that inhabit or seek Guanabara Bay to feed or reproduce, include the following species:
- Sea turtles
The bay was part of the migratory route of the whales who sought its warm waters to breed in the austral winter. By the eighteenth century, the frame (fishing) Whale was an expressive activity in the Guanabara Bay.