The far side of the moon isn’t just barren lunar landscape: what is it, and why did we stop talking about it?

Basically the title. I was about 10 years old when I saw an article or video about a structure on the far side of the moon. It was the last time I had heard anything about it. I’m not even sure if it was real or just some far out theory. If I remember correctly it was pictures of a large rectangle sticking out of a crater. If we had established bases or colonized the moon why did it never come to fruition?