I found this tube and wondered which animal built it.
It is 2 cm long and has an entrance/exit hole on one side. The material seems to be sandy.
I assume it is for breeding purposes.
Before finding the tube, I saw an unfamiliar kind of wasp around (could also be a hornet), with very long black legs. However, I could not find a wasp or hornet that builds such tubes, so it could be unrelated.
Location is Germany.
My questions are: which organism built this structure and should I expect anything crawling out one day? Or is it unfinished, since the entrance isn't closed?