Wien (Vienna) is the capital of Austria and located in the lowlands at the northeastern end of the county. The Alps end right south of the city. The underground is a Mesozoic basin full of about 4 km of sedimentary rocks like limestone, sandstone, marl and more. The city was the capital of the Austro-Hungarian Emire for centuries. Like any large city with a long history it has numerous artificial underground sites, subterranea which were built for various reasons and are now open to the public.