"Project Hush" is a top-secret project of US government - to build some sort of anti-nuclear-weapons system. It involves being the first to go to moon, & to set up some sort of military base there. And doing so in complete secrecy.
All goes well with the landing. A little scouting around their base's ("dome") location reveals yet another, already existing, dome! A scout is sent to find out more, & finds something astonishing...
Fact sheet.First published: Galaxy, February 1954.
Related: Stories of William Tenn, from 1950s.