As a very young SF fan I loved Space 1999. Later I grew to understand how silly the main plot device of the show was, but I still like the designs of the lunar structures and various space vehicles. The designers and model builders managed to capture a realistic look that seemed to extend the Apollo era technology as well as obviously borrowing from Stanley Kubrick.
And I think it had further influence; the new uniforms introduced in Star Trek: The Motion Picture appear to owe some inspiration to the Moonbase Alpha uniforms.
I recall seeing Landau in lots of things, but Commander Koenig is the character which I most fondly remember.