Oldest formation occurs in the center of an anticline.
Used in building. The youngest rock is at the center of a syncline. This outer doorway opens onto a corridor that travels a gentle upgrade for 16 miles. Once you reach the interior doorway, you'll find you're on the edge of an enormous valley, completely surrounded by high mountain peaks. This valley extends approximately 25 miles across, point to point crossing, with several small mountain ranges, rivers and a continuous flow of rolling hills.