The park of Peneda Geres in Northern Portugal is one of the most beautiful places in the world.
This site consists of finalised pages of information, and semi-public blog posts which are my notes of places I've been and walking routes. I produced most of the content back in 2012/2013 and am just updating now (2018).As shown on the map left, the Park curves around a portion of Portugal's northern border with Spain and the park continues over the border to form a Transfrontier park with the Spanish park of Baixa Limia - Serra de Xures. The Spanish side is a protected natural area, not a national park, and generally there is less infrastructure or information on the Spanish side.
The map below is taken from the display boards inside the park. On it you can see that the central eastern area of the park - the Serra of Geres (shown on the map as the large area in dark green) is highly protected and uninhabited. This area consists of remote high mountains that generally need special permissions (and skills) to enter far into it. A few paths will take you into the edges of this area, but not across it.
What you can visit, though, are the many beautiful hills and mountains around the Serra de Peneda (the West side of the park) and the villages that skirt the Serra de Geres. The villages and rural life is also incredibly beautiful - traditional villages in the area are built from deep granite blocks, nestling among oak woodlands in deep valleys. There are also high villages - called Brandas - traditionally used only in the Summer - which nestle improbably in the mountains.
The most developed tourist infrastructure is to the South East of the park in the villages of Geres. The Serra de Peneda in the West is less high, and less remote feeling - though still with many beautiful walks and villages, and the small towns in the area are definitely also worth visiting. The far east of the park, is the least accessible (takes longest to get there from Porto or Braga, fewer buses etc) but is very lovely.