The famous village of Castleton is the start and finish for this walk. Castleton's series of show caverns attract huge numbers of visitors each year, but even if it didn’t have the caves, the area around Castleton would merit a visit.
Church of St Mary and All Saints in Chesterfield, Derbyshire, is commonly known as the Crooked Spire. It served as the "in"spire"ation" for the church with the twisted spire mentioned early in The Sphere of Septimus http://simon-rose.com/books/the-sphere-of-septimus/
Another Celtic Cross monument similar to the one in the story described as standing on the village green in Middle Wogglehole in The Sphere of Septimus http://simon-rose.com/books/the-sphere-of-septimus/