When we were on the rafting trip, the water levels were high and we did not complete the usual course, so I'm not sure if our changing facilities were the norm, but on our trip there were two tents, one for men and one for women. They were set up in tall grass and they were just empty tents. Many of us were wearing wet suits and it was very difficult to change, put on your shoes, etc., with no place to sit and nothing to hold on to. Not ideal changing accommodations, but better than wearing wet clothes. If you like desserts, try the panna cotta (if they still offer it) from the lunch buffet in Ollantaytambo. It was delicious.