Remember this WIP? So this is aparently what I imagine a secret underground lair would contain in its various rooms.
It's always very important to stock up on Penny-Farthing bicycles, Erlenmeyer flasks, and test tubes of all sorts.
Also key is the closet-o-superhero/villain-outfits, for the extrapowered adventurer on the go.
Finally, remember to allow for a portal to the sky when including a rocketship.