You can go beneath the baths into the small and winding dungeons, where the heating system and water retention has been. It's not really spooky, but not really canny either.
but remember: don't go towards the light! =)
This has been a public toilet facility (latrine).
People were sitting close to each other on maybe marble desks with holes in them. Beneath there must have been water running to dispose the droppings...
this seems very eloborate.
If you venture to Ostia Antica to see the ruins - you could park up toward the town Piazza and see the local people and their homes. It is just a short walk to the ruins.
Go off the main paths and explore the houses, gardens and courtyards. You may be surprised at what you find. This beautifully-carved coffin was tucked away ..... I found it by accident.
Explore some of the houses and you may see the remains of the Roman central heating system.............underfloor heating and box tiles to carry warm air through the walls.