Megascale Engineering

Engineering projects that dwarf the imagination, most megascale projects would cause the average left-wing environmentalist to run screaming in terror. Forget about building a dam that may flood wetlands--there have been proposals floated¹ for the construction of a 20 mile high wall around Florida to deflect hurricanes from population centers.

Some commonly mentioned megascale projects are:

Terraforming

Alter another world to more closely match our needs. In principle it's no different than building a house or stitching animal skins together to make a blanket; in practice it probably can only be called an environmental nightmare and an ethical dilemma of immense proportion. Available to late type 0 civilizations (such as ours).

Space Elevator

A 20,000 mile high cable with a large asteroid hooked onto the far end to act as a counterweight. Almost certainly available to type I civilizations, probably not available to late type 0s.

Dyson Sphere

A shell made up of billions of floating islands of matter surrounding a star in all dimensions. This configuration allows a civilization to trap something very close to the complete energy output of its primary. Available to type II civilizations.

Stellar Husbandry

Treating stars as we presently treat plants. Probably not available to any civilization short of a late type II.

Jupiter Brain

An "individual" whose computational structure requires a computer with the mass of Jupiter. Such a creature would be of a complexity so vastly greater than that of a human that it is hard to comprehend. Available to advanced type IIIs.

1- Where "floated" is taken in the same sense that proposals for the construction of a Dyson sphere have been floated.

Back here on Earth, there are also some sizable Engineering projects that are either under way, or planned:

1. Back during the cold war, the United States looked into getting a Peace Dividend out of its nuclear weapons in terms of large-scale earth-moving capability. Codenamed Project Plowshare, the idea was to use nukes to carve out new harbors where none existed before. I seem to remember that the Soviets actually did use this method once, with spotty results.
2. And speaking of nukes, the Chinese have looked into using them to blast a hole through the Himalayas in order to divert the output of a large river onto Chinese soil. As the river currently irrigates much of northern India, this has the Indians worried.
3. And speaking of the Chinese, let's not forget the Great Wall of China, which was (and I think still is) the largest structure ever built by humans...and back in antiquity, too!
4. Hong Kong's new airport might also deserve a mention here. Since there's not enough real estate on the island to handle the necessary air traffic, they're building the whole thing on a new man-made extension to the island.

Ok, now back to the sci-fi. In addition to the space elevator, Kim Stanley Robinson's Mars trilogy also makes use of a soletta to heat Mars to more terrestrial levels. This is basically a really really big array of orbiting mirrors, focused on a central reflector of about 1/2 degree diameter as seen from the surface. The result is an earthlike sun for a planet farther out in orbit.

Kind of a spoiler follows.....

Later in the series, the soletta is removed from martian orbit, and becomes an enormous parasol for Venus, as the first in the terraforming of that planet.