Trasparenza, by Andrea Greenlees, originally built for Burning Man in 2016. It has transparent benches inside, but it looked a bit of a tight squeeze, so I left the children of the family that arrived a couple of minutes later to it. They seemed to enjoy exploring. There's a view from the inside on Andrea's Instagram.
GPS Coordinates:
51.44266, -2.63897
Location: Ashton Court