(boulders/rock) from the volcano's submarine eruptions were used in the construction of the forts and defences along the coast of the islands. Writing in his epic tome Saudades da Terra, the humanist theologian Gaspar Frutuoso, while describing Angra: "...what makes it very beautiful, the great high mount called Brasil, as I mentioned, it is all covered in pasture, some farming (which had been covered in trees)...encircled on all four sides, two small two large, this a caldera". Between the 16th and 17th century, the construction of a system of fortified structures that would be the nucleus of the Fortress of São Filippe/São João Baptista do Monte Brasil. Its main fortification hugs the northern slope of Monte Brasil, but includes of redoubts, emplacements and garrisons around the flanks of the volcano, including the Fort of Zimbreiro, Fort of Santo António, Fort of São Diogo and Fort of Quebrada. Many of the road accesses to Pico do Facho, Pico das Cruzinhas and Pico do Zimbreiro, in addition to the caldera and coastal forts were opened during this period, giving access to most of the peninsula. On Pico do Facho, starting in this period and extending to the 20th century, was a house and semaphore signalling post along with several military structures, including excavations in the ground (channels and rectangular depressions) representing complex installations associated with these activities. In the 19th century, the area around the Fort of São Diogo was improved and remodelled in order to support the construction of military batteries, during the Liberal Wars. At the beginning of the Second World War, structures were constructed on the summit of Monte Brasil to support coastal defences of the Azores, during a time when open warfare existed between the Allies and Axis. Buildings to garrison troops and munitions, including several artillery and anti-aircraft emplacements were established to protect the city from assumed submarine/naval attacks on Pico das Cruzinhas and Pico do Facho. In order safeguard the dynamic ecosystem of the region, the regional government established the Nature Park of Terceira (on 20 April 2011), that included the classification of Monte Brasil for the protection of the marine environment. The [TR20] Área Marinha Protegida de Gestão de Recursos do Monte Brasil (Protected Marine Resource Management Area of Monte Brasil) was established to protect the biodiversity of the fauna and marine habitats that included areas of submerse and semi-submersed grottos that exist along the