Twenty years ago, the most ambitious construction project in the history of the human race began with the launch of a Russian Proton rocket on Nov. 20, 1998. The uncrewed vehicle carried Zarya, a control module that would become the first piece of the International Space Station placed in orbit.

The first crew, consisting of American astronaut and former Navy SEAL Bill Shepherd alongside Russian cosmonauts Sergei Krikalev and Yuri Gidzenko, would arrive to live in orbit just under two years later on Oct. 30, 2000.

Construction of the ISS, however, would continue for another decade until 2011, when the final planned module was installed. All that assembly was done over a decade while the station was continuously inhabited by rotating crews of astronauts from several different countries.

NASA

"The space station to me and the way we have put that program together with our international partners is absolutely the best example of how we can peacefully, successfully do complicated things," retired NASA astronaut Nicole Stott told me via a teleconference earlier this year.

Stott spent three months living on the space station in 2009 and was also part of the final space shuttle mission in 2011 that delivered the last main section of the ISS, essentially completing its construction.

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A crazy construction project

"The International Space Station's supreme achievement is its construction," writes David Nixon, an architect who was invited to work on the design of the ISS, in his 2016 book International Space Station: Architecture Beyond Earth.

He points out the unprecedented hurdles involved, beginning with launching every module, nut, bolt and piece of framing required aboard a powerful rocket to a remote, empty and lethal location.

"Performing just one of these voyages safely was a major challenge but the station's design called for 30 of them just to deliver the station's basic building blocks. Against the odds, all arrived on orbit safely and flawlessly where they fitted together correctly and precisely."

Today the ISS is a six-bedroom research station with two bathrooms, a gym and a cupola providing epic 360-degree views. The station and its crew of up to six live and work while orbiting Earth every 90 minutes, traveling at a speed of 5 miles per second. It's powered by an acre of solar panels that help make the station relatively easy to spot from Earth.

When asked about the strangest part of living aboard a structure straight out of science fiction whipping around the planet at high speed, Stott said, "It really is that almost immediate reality check that we live on a planet ... In our day-to-day lives I don't think we acknowledge that at all."

Fulfilling a far-fetched fantasy

One of the earliest conceptions of a station in space was a "brick moon" described by Edward Everett Hale in his 1870 story of the same name. It describes a brick sphere, 200 feet (61 meters) in diameter, that's launched, somehow, using power from a waterfall and with people accidentally inside, making it one of the first references to an inhabited station in space.

By the middle of the 20th century, Soviet and American engineers were beginning to think more seriously about a place to live in space. The success of the Apollo program led to the launch of Skylab, which would be occupied by three crews for a total of 171 days between 1973 and 1974, paving the way for more permanent facilities in orbit.

This was followed by the Apollo-Soyuz test in 1975 that demonstrated spacecraft from the two nations, previously engaged in a heated space race, could successfully dock in space. The mission was a symbol of international cooperation and a harbinger of things to come, starting with the Russian space station Mir, built between 1986 and 1996.

A number of American astronauts would spend time aboard Mir, including some making the trip aboard the space shuttle.

Humans would leave Mir for the last time in 2000, just months before the first crew of the ISS would arrive to begin over 18 years of nonstop occupation that continues to this day.

One-of-a-kind laboratory

Over nearly two decades, the ISS has played a unique role in the scientific world as both an orbiting laboratory and Earth observatory. Much of the science and innovation done on the space station have had benefits for regular people on the surface of the globe.

For example, robotics developed for the ISS are being used for remotely operated surgical procedures, including for breast biopsies for women in remote areas.

Technology designed to test water quality aboard the station has also led to a mobile app to keep track of water quality in locations worldwide. Imagery taken from the ISS and elsewhere in orbit is also used to assist in natural disaster recovery.

One of the better known long-term experiments aboard the space station was the year-long investigation into the effects of living in space involving twin astronauts Mark and Scott Kelly. Scott lived for about a year on the ISS while his twin brother Mark stayed on the surface. Changes to both brothers were tracked meticulously to record how life in space affects the human body.

Life aboard the space station might sound a little uncomfortable with the lack of gravity, close quarters and required two hours of exercise per day, but Stott describes it as "the most comfortable I've ever been."

"I really wish everyone could experience it, just the ability to fly and float from one place to another and do what I only ever dreamed of."

The number of people who will be able to experience life on the ISS could be limited, however. The Trump administration has said it wants to cut off funding for the station by 2025. It's also been suggested that private industry might take over all or part of the operation of the ISS at that point.

NASA has made it clear it wants to continue having a presence in orbit and it also has designs on setting up shop at the moon, a plan that former ISS resident Chris Hadfield told me he approves of.

"Over 18 years ago we started settling space," says the astronaut who became famous for his microgravity rendition of the song Space Oddity. "The moon is the obvious, next logical destination."

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