Fort of São João do Arade The Fort of São João do Arade ( ) , sometimes referred to as the " Castle of Arade " , is a medieval fortification situated in the civil parish of Ferragudo in the Portuguese Algarve municipality of Lagoa . History . The first fortification on the site consisted of a watch tower erected in the reign of King John II of Portugal . Later , following the settlement of Ferragudo ( around 1520 ) , it is believed that the castle was encircled by a defensive wall ( built on the rudimentary walls of the older walls ) : giving rise to its original name " Castle of Arade " . The origins of the Fort of Arade ( or Ferragudo , as it is also known ) date back to the Philippine Dynasty , and the need by the Habsburg rulers to defend the coast of the peninsula from attacks by pirates and privateers in service to the Crowns of northern Europe . Yet , even at the beginning decades of the 17th century , no fortress was constructed owing to the indecision on whether to locate the fortification on the left or right margin ( location of Vila Nova de Portimão ) . Engineer Alexandre Massai defended a new construction in Portimão , while the left margin proposal ( in Ferragudo ) was defended by the municipality of Silves . According to a report by Alexandre Massai , the battlements already existed in 1621 , since he refers to “ um sítio cercado chamado Ferragudo ” ( “ a walled site called Ferragudo ” ) . The Portuguese Restoration War , once again , justified the construction of a new fortress . It was in 1640 that the order to construct a fortification came down from King John IV ; the fortress was built to substitute the Castle of Ferragudo ( ) which had lost its effectiveness . This bulwark was erected downstream on a rocky platform , but the effects of erosion and Atlantic storms ( especially a violent storm in 1669 ) caused severe damage to the original bulwark . Within four years ( 2 May 1644 ) , the first captain was assigned to the fort : Francisco da Costa Barros . The strategic location of this castle , from the beginning , made the fortress more than just a military structure . The fort controlled a privileged place at the mouth of the River Arade , with the capacity to strike as far as the margins of Portimão . An inspection carried - out by the " Governor of the Kingdom of the Algarve " , D . Rodrigo António de Noronha e Meneses , considered the fortification to be in perfect condition . At that time there were two artillery batteries : the " lower " battery , with three pieces of artillery ; and the " upper " battery , with four pieces . The 1755 Lisbon earthquake did not result in any damages , in comparison to many of the buildings / structures along the southern coast , partly due to its construction on soft rock . By 1821 , the fort remained active , referencing two , heavily armed batteries on its upper tier . The area was also a transit point for boats leaving the river , making it a responsible for fluvial traffic that entered and left Silves . But , this role was fleeting ; after the Concession of Evoramonte , the fort fell into disuse and was declassified in 1896 . Its history since then was of slow deterioration and abandon , that culminated in 1896 , with its public sale : it was sold at a public auction for 600 , 000 reis . Untouched throughout the 20th century , the group of structures maintained there state , waiting on rigorous studies and archaeological investigation . After its sale , it was adapted as a summer residence , by the poet Coelho Carvalho , who undertook extensive renovations to create a residence reflecting his personal taste . Still in private hands , it was classified in 1975 as a historic building by the Instituto Português do Património Arquitectónico ( IPPAR ) , forerunner of the IGESPAR . But , today , it is practically abandoned : the local authority petitioned for its transformation into cultural centre ; in 1976 , the " Junta Freguesia de Ferragudo " solicited the national government in order to occupy the fort . Architecture . Its location belies its status as a rural fortification , located on a hillock , overlooking the left margin of the Portimão estuary , isolated on a vast wooded property . Situated in a dominant position at the mouth of the Arade River , the elevated site divides two beaches : the Praia da Angrinha and the Praia Grande . Together with the Fort of Santa Catarina , on the water front of Portimão , the fort guards the estuary and mouth of the river . The plan of the fort is an irregular trapezoid , implanted on a high spot , with a keep and various spaces oriented to the sea . The vertical facades are covered with windows and barbican s . The structure of the fort is easily identifiable , with its battlements serving as positioning batteries . It was designed vertically , in order to permit visibility both from its battlements , and from sea . Its height , makes it one of the more interesting features of the structure , permitting observation . The site is well preserved , with a large walled garden stretching from Praia da Angrinha to Praia Grande , that includes a large residence .