The Wales Coast Path runs 870 miles along the entire coast of Wales.

The Slovenian Mountain Trail is a route of about 600km from Maribor to Ankaran. It covers most of the Slovenian mountain areas including Pohorje, Julian Alps, Kamnik-Savinja Alps, Karavanke and the southwestern part of Slovenia. It is the oldest hiking track in Europe.

An interactive map of the route is here. It typically is done from NE to SW.

Wikipedia: "Aneto [11,168' /3404m] is the highest mountain in the Pyrenees and in Aragon, and Spain's third-highest mountain, reaching a height of 3,404 metres (11,168 ft). It stands in the Spanish province of Huesca, the northernmost of all three Aragonese provinces, 4 miles south of the French border."