They look like pharyngeal cavities, like underground tracheas, like widely branched bronchi with fungi, dust particles and decades of deposits on the cell walls. “And yes, these places, which, in contrast to the representational spaces above, were never designed to be shown to the public,” says the Viennese author, curator and architectural historian Gabriele Kaiser, “do indeed have something anatomical about them. They are reminiscent of a huge organism that you have seen hundreds of times from the outside, but never before from the inside.”