Like most cities in Europe, Glasgow has a rich past. It was a small merchant town before the industrial revolution, and now, with 600,000 people, it’s the largest city in Scotland. We wanted to visit Glasgow for a unique idea that the Scottish government is developing to meet some ambitious energy goals. By 2015, the country wants half its energy to come from renewable sources. Five years after that, the goal is 100 percent.

Part of the answer may be under the streets, down in caverns more than 200 years old that were excavated for coal. As coal mining became too expensive in Glasgow in the 20th century, the mines were abandoned. The pumps that kept water from trickling