Vosges du Nord and Pfälzerwald have a number of points in common in terms of their ecology and landscape. They share three key words: sandstone, water, forest. The geological substratum (Vosges or variegated sandstone) is identical and explains the widespread forests in both areas. These forests consist primarily of three species, beech, Pinus sylvestris (Scots Pine), and oak. The relief is very similar even if Pfälzerwald has a higher average elevation than Vosges du Nord. The land from Saverne to Kaiserslautern consists of mountains cut by valleys with streams running over the sandstone, dotted here and there with artificial lakes. Numerous medieval, mountain-top castles and ruiniform rocks are to be found on both sides of the border.