A stone face watches over the river.

Central America's deepest lake is actually a volcanic caldera, surrounded by three volcanoes.

The farmhouse owned by the Danish author who wrote "Out of Africa" is now a museum honoring her legacy.

Get tall with nature's lankiest beasts and their warthog friends at this Kenyan preserve.

This Minnesota town celebrated the state's 100-year anniversary by creating a massive ode to nature's smartest bird.

Nine limestone rock stacks on Australia's "Shipwreck Coast."

A clear example of the process of erosion in action.

An opal mining town in the middle of Australia where people live, worship, and shop underground.

This eccentric cave dwelling is bizarre even by the standards of a subterranean town.

The longest fence in the world stretches over 3,000 miles to keep the dingoes out.

This trio of Australian rock spires may have inspired aboriginal legend or just modern tourism.

Built over an abandoned train yard, this hidden gem is full of winding paths and offers gorgeous views of Sydney Harbour.

Come for the flowers, stay for the bats!

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

The deepest metro station in the world.

The only visible reminders of an elaborate engineering project that kept the tower from reaching the tipping point.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

A morbid gateway to an Alaska town prides itself on the hunting history it represents.

A trading post in the North Pole where children send letters.

The king of U.S. high points towers over every other peak on the continent.

Siberian husky that delivered a life-saving antitoxin.

An Alaska livestock farm devotes itself to harvesting wool from creatures that once ran with mammoths and sabertooth tigers.