What would hinder the exploration of an alien outpost?

Let's say the dots on Ceres are abandoned alien outposts.
Within the next 40-200 years humanity manages to send a team of research scientists to the location. The scientists quickly found a way inside the base and are researching for several years now but with only moderate success.

The aliens used comparable technology: e.g. hallways, doors, data and power lines running in walls, etc. but they have a techlevel of around +1000 years compared to where we are now.

How could the aliens unknowingly built their base (without using weapons or deathtraps) so that our research scientists will need a maximum amount of time?

I'm especially looking for facilities of incomprehensible functions and/or special areas/features built into the alien base.

EDIT:

Answers will be accepted based off of how scientific, and realistic they are.

posted over 9 years ago

CausticHarmony‭

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