The European Space Agency and architectural firm Foster + Partners created what may be the most realistic and plausible design for the first habitable Moon Base. What is most interesting about the design is that a key feature involves 3D printing the structures using robots and moon dust...
90% of the stuff we need to build the base is already on the Moon, we only have to ferry the 3D printing robots (you can look at one below) and the lightweight parts, like the inflatables and the solid connector and entry segments. This will make this idea a lot cheaper than the alternatives.
Xavier De Kestelier of Foster + Partners Specialist Modelling Group says that their construction 3D printing technology has already produced entire structures under extreme conditions on Earth, so it's perfectly reasonable to do the same up there.
According to Enrico Dini—the founder of UK-based Monolite, who started to work on 3D building printers back in 2010 and proposed them for lunar base construction—the machines are now printing at 6.5 feet (2 meters) per hour. He says that their next generation will speed up to 11.5 feet (3.5 meters) per hour, which is enough to complete an entire building in one week.