At 230 height on Pico hill, with entrance through Rio Branco Baron Fortification, lie the ruins of the architectonic complex, which in the 18th century sheltered Pico or São Luiz Fortifications.

In 1715, the construction of Pico Fortification begins; its facilities are inspected by Marquis "Marquês do Lavradio", and the fortification is authorized to operate in 1770. In 1775, São Luiz Fortification is founded by the same Marquis, with the following distich on the entrance gate: "Josepho I. Imperante, Fidel.mo Portugaliae Rege, Provident.mo Príncipe, Arx Haec, Divo Aloisio Sacrata. Fundata est. 1775". In 1891, at the same period when Brazilian fortifications were disabled, both fortifications are connected thus becoming one single complex denominated as Pico or São Luiz Fortification, indistinctively.

This fortification, taking in consideration its height and location, protected the border's entrance, the entire Guanabara Bay and Santa Cruz Fortress from eventual attacks. However, the mostly known military act takes place in the Republic period during a rebellion leaded by 2nd Sargent Silvério Macedo on January 1st of 1892, with the intent to return the government to Deodoro da Fonseca. Rebel troops take over Santa Cruz Fortress, release the prisoners, take possession of cannons and all armament and imprison the officers, beginning to shoot against Laje Fortress. Two battalions leave Pico Fortification and seize the rebels that had already been bombarded from the sea by the ships commanded by the Minister of Naval Force himself, Admiral Custódio de Melo. Later, this Admiral leads the Armed Uprising and is defeated exactly by the troops of Santa Cruz Fortress and Pico Fortification, which remained loyal to Floriano Peixoto's republican government.

In 1918, with Wenceslau Braz as the President of the Republic, another fortification's construction was completed on the top of the hill - including modern and efficient 280 mm howitzers imported from Germany but deemed as obsolete in 1965, and the fortification was eventually disabled.

Currently, Pico construction still maintain with imposingness and grandiosity stone watchtowers and walls covered with vegetation, two imposing access gates, corridors, galleries and tunnels full of mystery and wide rocky courtyards. From the top of the hill, you can see on one side Santa Cruz Fortress, Urca Hill (Morro da Urca) and Pão-de-Açúcar Hill; on the other side Imbuí Fortification and the infinite Atlantic in a dazzling view.