Arthur C. Clarke postulated...

In The Exploration of Space (1951), Clarke uses this fantastic painting by Leslie Carr to illustrate what a permanent lunar colony would look like "one hundred years in the future" (c. 2051) with the aid of atomic power.

Railways will be extensively used, he says, as a smattering of colonies like this one would begin to change the face of this world. Is there a dome around this that we cannot see? Seems like there must be if greenery is there.

What kind of dome could it be?