The room is warm and sort of moist, but not actually damp. I'm pretty sure it's underground. The lights are kind of dim, but they aren't all on, so it could be brighter. There is a nice, overstuffed reddish-brown couch, and a green shag rug over most of the cement floor. There is a TV and a kitchenette, but mostly the room is full of bookcases and various games. I'd guess it's a rec room, but I've never actually lived anywhere that has one.
The trees are mostly pine, and some manzanita. It's dark, except for clearings that are almost unbearably bright. The ground is reddish and spongy, like decaying trees, and there are a lot of fungi and mosses.
The path isn't maintained or paved, but it is visible as a two foot wide strip where nothing is growing and footprints can sometimes be seen. There are occasional gum wrappers and other detritus along it. It's pretty easy to walk on, although there are sometimes roots along the way that would trip a daydreamer.
It's a natural lake, with a bit of a beach that's mostly pebbles. The water looks kind of suspect, and although there's a floating platform in the middle of the lake and areas roped off for swimmers, there's no one in the lake besides a few canoes and far-off fishing boats.
It's a sports bottle, not overly large but not a kiddie size either. It's a pearly turquoise color of plastic, with a black lid and a black straw. The cap to the straw has been torn off. It has an advertisement silk-screened on it.
The key is a warm bronze color, and looks well-used. The handle part is angular, sort of pentagonal. I'd guess it unlocks a house, or a cabin by this lake.