I got the Varia Suit and found the Map Room in Norfair. Unfortunately, nothing else appears to be accessible. The most spoiler-free help you could give would be appreciated.
Thread title:
Varia protects from heat, so you can assume that now the only obstacle in your way is a hot room. That narrows down your search to one area, and the passage(s) has to be in some room you've already visited. It's a little bit hidden, but not in some difficult way.