Military maps, produced by the Portuguese Army’s Geographic Institute (Instituto Geográfico do Exército – IGeoE), are available at scales 1:50.000 and 1:25.000, are the most detailed maps you will find in Portugal.
Similar to UK Ordnance Survey maps, but they come as one large sheet on fairly thick paper, more suitable for hanging on your wall than putting in your pocket when you want to go off exploring!