Black Gold: Oil City, Pennsylvania

Nestled in the Allegheny Mountains, Oil City might just be the most relevant small town in the world today. Here lie the remnants of the world's first commercially successful oil wells, dating from the 1860s. This former boomtown and the surrounding forest demonstrate how man's relationship with fossil fuels has been disastrous from the start. In the middle of town, the Allegheny River is joined by Oil Creek, and history overflows.

Hiking trails surround the town, and you'd never know that Oil Creek, meandering lazily through the rolling hills, was once the site of mass industry – and massive pollution. The soft ground underfoot has given way to new growth since the last oil wells were closed down, but the musty smell of old wood and rusting metal still lingers.

Plaques along the trails depict historic moments and sites: Edwin Drake's original commercial oil well, for instance, and the point where the stream was once dammed (when that dam was dynamited, a man-made tidal wave propelled skiffs loaded with oil barrels downstream, piloted by prospectors with dollar signs in their eyes). A plaque shows the location of a once world-famous gusher, which produced oil faster than barrels could be made to contain it; oil overflowed into the little stream and blackened the water. That spot is now a thicket of briars and red berries.

The 7,100 acres of state parkland surrounding the stream provide lively hiking and the three-sided Wolfkiel shelters for camping, at two and seven miles from the main parking area.

But the real treasures await an explorer willing to venture off the beaten path. Remnants of oil drilling operations still pepper the steep hillsides around the foggy valley. Multi-story wooden shacks and century-old slabs of concrete conjure images of bustling industry – of fortunes built at nature's expense, and so often lost at her whims.