I discovered this on Saturday during a trip to a ranch near Kerrville, Texas, in rural Gillespie Country.
Isn’t it great?
That’s epoxy-coated rebar holding up the old bottles in an old live oak trunk. I couldn’t see down in it very well, but given the stability of the rebar, I assume someone poured concrete into the trunk to hold the rebar in place. (I only saw one broken bottle.)