Pole in hand, a boatborne river Bushman hovers above the waters of the Okavango River in Botswana, Africa.

"You can see all the ingredients," photography expert Gerd Ludwig said of the circa-2004 photograph by David Doubilet. "You have plants, water, and you have a person, light, shadowyet it's very mysterious. I find images that do not explain everything right away more intriguing."

Ludwig's work appears inside and on the cover of the new National Geographic book Wide Angle: National Geographic Greatest Places. Here he offers his thoughts on ten images he selected to represent the diversity of the collection's 260 featured photos.

Encompassing all seven continents and more than a century of photography, each image in the book captures a location's "sense of place."

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