Roman Baths: Basic and No Frills
Berkeley Springs has historical significance, being a spot of local mineral waters that the country's founding fathers bathed in. Today, you'll find spas all over town offering treatments with these waters, but the Roman Baths at the state park are some of the cheapest.
That said, these baths are quite basic and no-frills. Essentially, you'll get a private room with a big bathtub (easily big enough for 4) filled with hot, mineral water. There was no bench in the pool, so you couldn't really sit while soaking (the stair entry wasn't quite conducive to sitting for more than a minute or two).