There is not way those are glued together - too much weight - my guess is that there are holes drilled into the stone and metal poles inserted, then possibly glued for additional support. By choosing the right contoured stone the metal pole would be invisible.
The picture attached are three decorative stone cairns I built, each stone has a drill hole through it and a 1/2" threaded aluminum rod going up through them. The stones are supported with a large cobblestone base (that also has a hole drilled through it) and under that are some washers and a nut to keep them at the right height, that are buried in the ground. The aluminum rod is 5' tall and the cairns are 4', 3.5', and 3' tall. The extra lenght is in the ground for more support.
That is a nice project that I will attempt to tackle with the supply of beach stone I have collected for stone art that catches my eye. It looks like the stone as been painted with a clear acrylic, not keen on that look. It is 15 degrees out there so it will have to wait till it warms up a bit.
