The Allerdale Ramble is nominally a 87km / 54 mile long distance path (LDP) starting in the Lake District National Park before striking out west for the Solway Firth coast.
We say "nominally" as the key word here is "ramble": the walk designer, Harry Appleyard, gives you options at various points, the most significant being whether or not you scale Skiddaw. And even there if you do choose to climb that mighty hill he suggests several different routes you could use all of which fall within the Ramble.
However the essence of this walk is that it starts at Seathwaite south of Derwent Water at the bottom of Borrowdale and it takes you back up Borrowdale and along the west side of Derwent Water to Keswick. Here you get to choose whether or not to climb Skiddaw but either way all options end up with you walking along the north east side of Bassenthwaite Lake and then on towards Cockermouth. (source: Allerdale Ramble