Sewer, gas, water and electricity mains, cable TV and telephone lines, fibre optic cables, water tubes, traffic control systems, street lighting, culverts, heating networks, transport systems, data cables, drainage, etcetera... Developments of the past century have turned the public subsurface into a maze of widespread, dense utility networks. Without us being constantly aware of it, webs of utilities are spun beneath us. The total value of these assets is estimated at hundreds of billions of euros in the Netherlands alone.