Earliest tunnels were home improvement projects; cave dwellers
appear to have thus enlarged their living quarters. But the
ancient Babylonians may have been among the first to use tunnels
for irrigation, in addition to building a passage from palace to
temple under the Euphrates River. Tunnels have advantages beyond
their ability to connect distant points. Environmentally, there
are benefits to placing transportation underground where
emissions can be more easily captured and treated. If tunnels
are re-imagined as tubes, floating throughways may one day
transit straits and even oceans. Building the World Blog by
Kathleen Lusk Brooke and Zoe G Quinn is licensed under a
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
License.