Esther, I have a friend who got me on a new crafting kick (as if I need ANOTHER craft to clutter up the place around here, and get started but never finished).
Anyway, she has taken colored glass objects - vases, tumblers, plates, etc. - and used water proof glue to stick them together, and is using them like a bottle tree. She puts a tall skinny one on the bottom, and adds other ones stacked on top, and then slips the tall skinny one over a stick that's pushed into the ground, in the fashion of a bottle tree. Light coming through the various colors of stacked glass is really pretty, and more interesting than a single bottle.
Here in Houston, trapping humid air inside the glass is a problem, as it may be nice and clear when the craft is made, but setting it in the sun can cause the moisture inside to condense and form drops inside the vases. She places the objects upside down, so they don't trap rain, and uses a solid ring of adhesive, but moisture can still get inside, too.
Wish I could post a photo. They are stunning.