How big could an alien-made object on the far side of the moon become so that discovery still can only happen by accident?

A great way to introduce advanced technology to a story is to have it be of extraterrestrial origin. E.g. have a spaceship crash on earth, or, like I was planning to, put a derelict spaceport on the darkfar side of the moon and have humanity discover it by accident.

What I mean with by accident is having humanity progress far enough to set up things such as a moon base (complete with its own space elevator), a research habitat orbiting mars and regular traffic between these & earth.

Then have someone discover, accidentally, an object on the far side of the moon that is just too regular to be natural (be that from space, or from an expedition on the far side itself).

Now the thing is that I do not want that discovery to happen too early. E.g. by rockets circling the moon or similar.

Q: How much surface-area can I give my derelict alien spaceport to prevent it from discovery through routine measures?

posted over 7 years ago

dot_Sp0T‭

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