There are hourly tours of the powerhouse. You are taken by bus down into the canyon and up along the river towards the base of the dam — we saw a moose and a bald eagle. The bus stops at the base of the canyon wall and a huge door rolls up. The bus drives into the tunnel and about half a mile straight into the mountain. The chambers and tunnels are so huge there is no sense of claustrophobia, of being in a cave deep underground. Then the group proceeds on foot through a smaller tunnel to the generator room.