Seemed very sturdy. It looked like the anchors attached to the trees were cored completely through the trees. The ramps up were concrete foundations with solid looking wooden scaffolding towers. The floors were either wooden planks or a concrete/glue composite material. The suspension bridge parts were suspension cables anchored between trees holding up composite plates bolted directly to the suspended cables. I'd estimate the cables were thick enough to hold several thousand pounds.
It is pretty solid and sturdy but most if all Safe.
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