It's white, sterile; the temperature is moderate and comfortable, and the walls bend around instead of having corners. I also experience a sense of deja-vu. There is a stool in the "corner" of the room that is painted on top with the symbol of a Yin-Yang, minus the black/white dots.
The trees I see are spaced closely together, and are tall and Evergreen. The wood is wet and smells of rain in a fresh air environment.
The trail itself is made of mulch, and it's padded down in places as though something very large and heavy had walked that way ahead of me. It seems to be the only navigable corridor through the trees, as they are too close together to facilitate any other ingress or egress.
The water is a stream, quickly-flowing and gurgling as it dashes against rocks that look as though they were cut by men and then thrown in the water. The water smells cool and fresh, and would be clear enough to see to the bottom were it not so swiftly running.
It is a green, long-necked bottle (one that looks as though it would be corked), and the outside bears the faint marks of a label (and someone subsequently having scratched it off).
The key is relatively small, and is the color of rusted bronze, with faint fletches of rusted copper. It's one of the old-fashioned kinds of keys that looks like it would open a cell door, or a gate, or something.