I did this and I chose my parent's back yard because I would always sit and relax out there and just listen to the birds etc.. and it was where I spent tons of time with my dogs.

However one dog passed away since and was buried out there so I wont even go in the yard now, so I had to change it but I've not thought of anything new yet.

He told me alot of clients visualize places like the beach or some place where they feel calm and at peace, maybe a library or something