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."

sanderson posted the route:

The Capital Ring is a 78 mile (126km) path around London, linking up parks and green places. It officially starts at Woolwich Foot Tunnel but the circular nature of the path means that it can be started and finished at any place. I have researched an FKT for this path but as yet have been unable to find any record of an attempt. 

Mick Warwick posted about a possible FKT:

The Ribble Way is a 73 mile footpath following the River Ribble along the beautiful Ribble Valley from its mouth to its source. The footpath traverses the counties of Lancashire and North Yorkshire and is divided into 7 sections each approximately 10 miles long.

Sam Anderson posted the route:

The Lee Valley Way is a 53 mile route along the Lee (or Lea) River from its source in Leagrave, Luton to Leamouth at East India Dock, where it runs into the River Thames.