In Great Britain, those traveling by rail must heed the warning to “mind the gap,” that is, to be aware of the space between the platform and the train where a person could trip and fall. In Pittsburgh, travelers, adventurers, and even historians should also mind the GAP, that is, they should be aware of the gorgeous 150-mile biking and recreational trail known as the Great Allegheny Passage.

This episode is also available as a blog post here.