It's about 100 km long - many hiking trails. This trip needs either a mountain bike or hiking shoes :P
It can be a good combinaison trip - cycling and hiking parts.
Directions: follow from Kockelscheuer the trail "sentier du Sud" followed by "sentier des mineurs".
The Red Lands (Luxembourgish: Minett, French: Terres rouges, German: Roten Erde) form a geographic region in southern and south-western Luxembourg. They are so-called the for their red iron-laden earth. Read more on Wikipedia
The way back to Luxembourg is the cycle route PC12, followed by the PC13.