Flysch Zone, the geological zone located on the northern edge of the Eastern Alps stretching from Vorarlberg to Vienna, mainly made up of sandstone (also called the "Sandstone Zone"), in addition to the marl and lime marl of the Cretaceous and Late Tertiary periods. In the south the flysch zone borders on the Northern Limestone Alps, which were pushed under the flysch zone in the late phase of Alpine mountain formation in the Early Tertiary period; the Molasse Zone, which includes the Alpine Foreland was pushed on top of the flysch zone. The rock of the flysch zone appears in places in geological "windows" within the Limestone Alps ( Brettlfenster, Windischgarsten Window) and was found in the course of deep drilling under these areas (Urmannsau, Berndorf). The Austrian flysch zone forms the northern portion of the Pre-alps and is circa 10-15 kilometres wide. It is at its widest in the Vienna Woods (approx. 20 kilometres). The rolling hill region with peaks reaching to just over 1,000 m (Pernecker Kogel mountain, Upper Austria, alt. 1,080 m; the somewhat smaller Hochpyra mountain in the east, alt. 762 m, Schoepfl mountain 890 m) is thickly forested and characterised by scattered farms.