There is an underground power station right next to Lake Manapouri. It uses the water out of Lake Manipouri which is then released into the Tasmanian Sea. Lake Manapouri it 200 meters (600 feet) above the sea level and gets plenty of rainwater to keep its level nearly constant throughout the year.

To visit the power station our bus traveled through a long tunnel that not only went down, but also circled around so that we ended up more or less directly below where we entered the tunnel. Below is an illustration how this power station, providing 15% of New Zealand's electricity, is situated