I guess to me a power place is where you want to settle down for a bit, spend some time with THE PLACE. Some one said it re-energizes you. That's very close to - is for me. A sense of history, and you meshing smoothly with that history with honor and respect. You become more aware of your surroundings, notice subtle things. A slowing of movement, deliberation.
Hell, it doesn't even have to be pretty. Hueco Tanks is 20 miles outside of the hole, El Paso, and the history, climbing and charging energy of the place kept me wholly in thrall for two months.
Erik