Moreover, dual U.S. and Canadian approval, inhospitable terrain, environmental concerns, long-term financing and tunnel administration will need to be adequately addressed.

CENTERFORSECURITYPOLICY: The Bering Strait Tunnel Project

Land-locked Bolivia is the poorest country in South America and outside the main cities much of it is barren and inhospitable terrain.

BBC: NEWS | Americas | Rains hamper Bolivia flood aid

Expected to be there for a short period, UN troops are operating in some of the most inhospitable terrain in the world.

BBC: NEWS | Africa | Q&A: Horn's bitter border war

Individuals, families and communities pitted courage, determination and resourcefulness against all manner of obstacles, privations and dangers: inhospitable terrain crossings, brutal weather, unrelenting hunger, ravaging diseases and hostile encounters in lawless lands.

FORBES: In Reflection, With Resolve, Rediscovering American Exceptionalism

Hidden in the jungle for more than a thousand years and only accessible by a 44km trek through inhospitable terrain, visiting Ciudad Perdida gives travellers the chance to live out their Indiana Jones fantasies as they battle rock scrambles, steep ascents and numerous waterfalls along the way.

BBC: Trekking to Colombia��s Lost City

The canyon was inhabited by native peoples as far back as 10, 000 BC, European explorers braved the inhospitable terrain first in the 1500s and then again in the 1800s, and the canyon became accessible to its first influx of visitors in 1901 when the Grand Canyon Railway was built to service mining claims.

BBC: Touring the American Southwest in a cowboy��s boots

The vast areas involved -- and some of the most inhospitable and scorched terrain on Earth -- make outside intervention risky.

CNN: STORY HIGHLIGHTS