The Rainforest Room is part of the Senses Spa on the Dream. It has an area with ten (10) heated tile chairs looking out onto a partially open verandah that has two 2-person jacuzzis. There are also four (4) showers that each serve up different combinations of warm and cool showers with different jets and shower heads. There are also three steam/sauna rooms, the Hamam (a Turkish bath), a Laconium (a dry sauna), and a Caldarium (a steam bath).
The Rainforest Room opens at about 5:00pm on embarkation day after the Sail Away party ends and keeps the same hours as the spa (8am to 10am).
On the boat, a 1-day pass is $16. On our recent 3-day cruise, the 3-day cruise pass for singles is $42. The 3-day couples cruise pass is $75.
The spa techs do say "there are only 40 passes available for the entire cruise", but whether this is just a marketing tool or real is unknown. We spent almost 8 hours in the spa on our cruise and only ever saw it crowded once.