A post from a Facebook group briefly explains a barrier free shower:
Here is a project I did a few years ago for a customer. It was part of a third floor master suite. They wanted a barrier free shower with a slipper tub in it. The entire 13′ x 13′ floor area is a waterproof shower stall. This is what can be done with Schluter Ditra and Kerdi. I exposed the chimney brick, installed a skylight and put LED uplighting on the beams.
Photos are from the original Facebook post.