urban agglomerations of Arcos de Valdevez coincide roughly with the principal roadway, the Estrada Nacional E.N.101, that links Braga with Monção. The construction of the ancillary I.C.28 altered this pattern, permitting rapid access to Arcos de Valdevez from other regional centres. Administratively, along with Viana do Castelo, Ponte da Lima, and Ponte de Barca, it is overseen by the VALIMA Associação de Municípios do Vale do Lima (Association of Municipalities of the Vale do Lima). Since 1981 the population of the municipality has been in steady decline; relative to the 2008 census, the population of the municipality has decreased, but at a rate far less than following the urbanization brought on by the Carnation Revolution in Portugal. The result has been an emigrant population, with most activities and residential concentration within a small area along the southwest border. Consequently, the urban areas of Salvador (with an urban density of 1090 habitantes/km²) and its neighbouring parishes (São Paio, Aguiã, and Giela) have seen some concentration. Architecture Civic Bridge of Arcos de Valdevez () - constructed during the nineteenth century, beginning in 1876 and finalized in 1880, to replace the medieval construction. The monument is composed of stone blocks in four arcs with ample lateral accesses in a Roman style that open to a flat platform. Castro of Ázere (), a fortified castro placement in Monte, erected during the Iron Age, but inhabited from the eighth century B.C.; Dolmens of Serra do Soajo (), a group of dolmen constructions, in various states of ruin, used by the ancient settlers of the region, in the foothills of the Serra do Gêres, near Mezio and Cabana Maior; Manor of Quinta de Aboim () - located in the parish of Aboim das Choças, is an example of a nobleman's eighteenth-century manor house; Pillory of Arcos de Valdevez () - in 1515 King Manuel I had this stone structure built in the main square, but it was moved in 1700 from the Municipal Square () to the river's edge, until finally being re-erected in a small square along a strip near the main church. In 1998, it was replaced in its present location. Designed by João Lopes, it is a single structure in the form of a twisted colonnade, surmounted by the Portuguese military sphere and national shield, atypical of common pillory use. Summer-House of Requeijo () - a manor house with a characteristic rectangular plan