Where are all of the pedestals?

Solution 1:

I was missing only one pedestal. The four pedestals, including the ones I mentioned in my question, are:

  • Two in the main room
  • One in the gallery
  • In the Alpine Skyway room, there is a door with a picture of a laboratory beaker on it. Just inside this door is a strange purple wall. Use the Dweller mask to get past it and find the final pedestal.