In 1555 at Fora Beach (Praia de Fora), which is currently known as Rio Branco Fortification Beach, an observatory was created that in 1567 was armed and turned into Battery with the construction of the first howitzers. In 1596, this Battery defeats the Hollandish squad headed by Van Noorth, and in 1710 Duclerc's French expedition.

In 1863, at Imbuí Edge, started the construction of the fortification named D. Pedro II, whose responsible was the military engineer Henrique de Beaurepaire Rhoan from Niterói, who was charged by the Emperor to execute a plan to improve the fortifications on the coast of Rio de Janeiro state.

The initial project included a terrestrial connection to Fora Beach's Battery, thus making it necessary to build another fortification, initially called Fora Beach's Battery. In 1893, this fortification receives the denomination of Marshal Floriano Peixoto Fortification, due to the decision made by military garrisons headquartered in the region aimed at defending the President. On November 25 of 1938, the name changes to Rio Branco Baron Fortification (Forte Barão do Rio Branco) as homage to the diplomat. At the front of the entrance are both cannons that fired against Duguay Trouin during the French invasion in 1711.

The fortification's construction - later called Imbuí - was interrupted for some years and resumed in 1893 for the Armed Uprising. Then the iron and nickel domes imported from Germany are placed, German cannons Krup are installed and the cannon towers are built. The constructor at that time used stonecutting from the seashore and consolidated with whale oil, lime from shells and shellfish. Finally, on May 24 of 1901 the Fortification's facilities are inaugurated - called Imbuí Fortification at that time - and now disabled for 21 years.

Both fortifications are connected through a small road surrounded by trees and beaches, and along with Pico Fortification they form a complex in a 3,200,000 m2 area, from which 2,800,000 m2 correspond to Atlantic Forest preserved areas, including zoological animals (sloth, sagoins, native owls, etc.).