Hierarchical overview

Hi everyone!
I am new to Omeka and I wonder what module makes this kind of hierarchical overview?
http://archives-bourbaki.ahp-numerique.fr/classification
Also any tips on the best ways of building multi-level hierarchies would be much appreciated. I am working with archives, so I would like to be able to easily place files inside of series, series inside of fonds etc.
Thank you!

Your link is a simple page with Omeka Classic (not Omeka S, no plug-in needed).

If you don’t need a semantic dimension, Omeka Classic is probably more developed. You can look at Collection Tree and Archive Repertory plugins, but I can’t advise you.

Ok, thank you! This is helpful.