Unusual request--looking for games that have hidden passages,secret panels,etc.

Tomco

So games set partly underground with puzzles that give you access?

Some ideas -- Riven, Timelapse, Nibiru.

The Black Mirror games also have them. These are on my mind since I've been playing them recently.

Nancy Drew - Blackmoor Manor

Traitor's Gate I

The older "Frankenstein: Through the Eyes of the Monster" has absolutely LOADS

It is older but Laura Bow: The Colonels Bequest.

Hi,
Riddle of the Sphinx, all kinds of hidden passages. Also it's sequel The Omega Stone.

I've spent a lot of time being lost in those two.

Charllotte

I'll second Riddle of the Sphinx.
Riddle of the Sphinx had a lot of secret passages in it.

You might also enjoy the RHEM games, which are full of secret panels, doors, and mysterious controls.

Agree with Jenny, Rhem 2 is totally underground, a real brain teaser, like all the Rhem games.

Cue I loved Traitors Gate! It definitely had lots of tunnels and sewers to explore!

and if I may add two games from Free Games Galore, try Dead Cyborg and Penumbra Tech Demo
even if this last one has a little action sequence.

Have fun.

Chief