A relatively easy and shaded walk in the Porto area of around 4 miles, is to walk down the gorge between the villages of Evissa and Ota.   The path drops down quite steeply initially, but then follows the line of the Spelunca river, crossing a couple of old bridges, before rising up to reach Ota.  The only drawback is the route is linear, so Jude offered to drop me off and I added on a little extra by walking all the way back to Porto.