The ramparts of the Moorish Castelo dos Mouros, captured by Christians in 1147, above the town of Sintra, Estremadura, Portugal, Europe

Tourist and church with blue dome, Oia (Ia) village, Santorini, Cyclades, Greek Islands, Greece, Europe

Tourist on roof of red church above the old town, Mykonos town, Chora, Mykonos, Cyclades, Greek Islands, Greece, Europe

Agricultural terraces , Machu Picchu, peru, peruvian, south america, south american, latin america, latin american South America. The lost city of the Inca was rediscovered by Hiram Bingham in 1911

Inca wall, Machu Picchu, peru, peruvian, south america, south american, latin america, latin american South America. The lost city of the Inca was rediscovered by Hiram Bingham in 1911

Typical street, yellow post-box and lady in black, Frigiliana, Malaga Province, Andalucia (Andalusia), Spain, Europe

Formal garden, historic castle, medieval village of Marvao, Portalegre district, Alto Alentejo, Portugal, Europe

Check dams crossing valley to control risk of flash flooding down steep hillside, Mirleft, Morocco, North Africa, Africa

Tourist on roof of red church above the old town, Mykonos town, Chora, Mykonos, Cyclades, Greek Islands, Greece, Europe

Backpackers look at the Inca ruins at Machu Picchu, UNESCO World Heritage Site, Peru, South America

Tourist and church with blue dome, Oia (Ia) village, Santorini, Cyclades, Greek Islands, Greece, Europe

The Great Wall at Mutianyu, UNESCO World Heritage Site, Beijing, China, Asia

Steep castle moat walls and waters with autumnal colors in fall, Osaka, Hoshu, Japan, Asia

Ephemeral Spring on Red Wall of Roaring Springs Canyon, North Kaibab Trail, Grand Canyon North Rim, UNESCO, Arizona, United States of America

Young woman standing on a defensive wall of Smbataberd Fortress, on the crest of a hill between the villages of Artabuynk and Yeghegis, near Yeghegnadzor, Vayots Dzor province, Armenia, Eurasia

Steep castle moat walls and waters with autumnal colors in fall, Osaka, Hoshu, Japan, Asia

A rock climber tackles a very difficult route on the steep walls of Gordale Scar, a famous limestone ravine near Malham Cove, North Yorkshire, England, United Kingdom, Europe

Corinth Canal connecting the Gulf of Corinth in the Ionian Sea with the Saronic Gulf in the Aegean Sea, Greece

A hiking path along a river in a steep valley with high stone walls, Oregon, United States of America, North America

Steep walls, autumn gold and red trees with steam from a volcanic hot spring, Hell Valley, Noboribetsu, Hokkaido, Japan, Asia

Taktshang Goemba (Tiger's Nest) Monastery, Paro, Bhutan, Asia

Mar Saba, one of the oldest continuously inhabited monasteries in the world, eastern Judean Desert, Israel

A view of a waterfall on the steep wall of mountains with the Myklebustbreen glacier at the top, Vestland, Norway, Scandinavia, Europe

Montserrat Monastery founded in 1025, Catalunya (Catalonia) (Cataluna), Spain, Europe

A view of a waterfall on the steep wall of mountains with the Myklebustbreen glacier at the top, Vestland, Norway, Scandinavia, Europe

The ancient Great Wall of China at Mutianyu, north of Beijing (formerly Peking)

The ancient Great Wall of China at Mutianyu, north of Beijing (formerly Peking)

The ancient Great Wall of China at Mutianyu, north of Beijing (formerly Peking)

The Drus, a famous rock wall on the Mont blanc range. The pale grey area of rock upper rightis new rock revealed by a recent, massive rock fall.

A frozen Stickle Tarn with crack patterns in the ice, above the Langdale valley with Pavey Ark in the background, Lake District, Cumbria, England, United Kingdom, Europe

Icicles hanging from steep rock wall, partnachklamm, garmisch, germany

A woman hill walker by a frozen Stickle Tarn in the Langdales, Lake District, Cumbria, England, United Kingdom, Europe

An instructor takes a young child for a lesson on the bouldering section of a climbing wall in Ambleside, Lake District, Cumbria, England, United Kingdom, Europe

Young children on a climbing wall in Ambleside, Lake District, Cumbria, England, United Kingdom, Europe

steep rock carved stone steps to Lotus Peak, Huang Shan, Anhui province, steep climb, stone steps, World Heritage, UNESCO, China, Asia

porter carrys building material on his back up steep mountain steps, Taoist mountain, Hua Shan, Shaanxi province, Taoist mountain, China, Asia

Climber roping in the fog, Tyrol, Austria, Europe

Climber at Schuesselkar rock face in the sunlight, Tyrol, Austria, Europe

A young woman climbing a steep wall above the sea, secured with a chain, Golfo di Orosei, Selvaggio Blu, Sardinia, Italy, Europe

Climber roping in the fog, Tyrol, Austria, Europe

Climber roping in the fog, Tyrol, Austria, Europe

Young women climbing in a steep wall, hiking and climbing on Mallorca, climbing area La Creveta, Cap Formentor, Mediterranean Sea, La Creveta, Cap de Formentor, Serra de Tramuntana, Unesco World Cultural Heritage, Mallorca, Spain

Child climbing in the mountains, Karwendel Mountains, Upper Bavaria, Bavaria, Germany

Monastery, Chossowiotissa, Amorgos, Cyclades, South Aegean, Greece

Wall of columnar basalt with waterfall Bridal Veil Falls, tropical vegetation, Pakoka River, Makomako, Waikato, North Island, New Zealand, Oceania

Climber climbing on a rock wall, alpine climb, Alps, below the summit, Petite Forch, Canton of Valais, Switzerland, Europe

Aescher tavern in the steep facing north flank of Ebenalp mountain, Appenzell, Switzerland

Aescher tavern and panorama mountain view in the steep facing north flank of Ebenalp mountain, Appenzell, Switzerland

Rock climber steep wall

Hikers in river, The Narrows, Virgin River, steep walls, Zion Canyon, Zion National Park, Utah, USA, North America

Red knot coral (Acabaria biserialis) in the backlight, on a steep wall. Dive site St Johns Reef, Saint Johns, Red Sea, Egypt, Africa

Tolmin gorge, gorge with moss-covered steep rock walls, wild stream with blue water, Slovenia, Europe

Giant sea fan (Annella mollis) on steep wall, St Johns Reef dive site, Saint Johns, Red Sea, Egypt, Africa

Kayaking under a glacial wall, Kenai Fjords National Park, Alaska, USA

Ruin Duernstein, rock landscape, Wachau, Lower Austria, Austria

Cap de Formentor, mountain road, Majorca, Balearic Islands, Spain

Hiker walks in the water, The Narrows, narrow place of the Virgin River, steep walls of the Zion Canyon, Zion National Park, Utah, USA, North America

Hemprichs tree coral (Dendronephthya hemprichi), red, on steep wall. Dive site Small Brother, Brother Islands, Egypt, Red Sea, Africa

View into a valley with rock walls in the mountains, Peloponnese, Greece, Europe

Karwendel Mountain Range between Johannestal and Lamsen Spitze, Austria. The Karwendel limestone mountain range is the largest range in the eastern alps. Large parts of the Karwendel are protected and a popular destination for tourists, hikers and climbers. Europe, Central Europe, Austria, Tyrol, July

Big wall climber Tommy Caldwell rock climbing Dihedral wall, a multi pitch route on El Capitan in Yosemite National Park, California.

Bruce Miller climbs on the hardest part, or "crux", of a route called "Jules Verne", rated 5.11a, high off the ground on the Redgarden Wall in Eldorado Canyon State Park, CO. Jules Verne is one of the more famous traditional or "trad" routes in the area, and has long sections between protection. Eldorado Canyon, located on the Front Range south of Boulder, and its steep, difficult sandstone cliffs attract climbers from around the country and the world, making it one of the most popular climbing areas in Colorado.

Bruce Miller climbs on the hardest part, or "crux", of a route called "Jules Verne", rated 5.11a, high off the ground on the Redgarden Wall in Eldorado Canyon State Park, CO. Jules Verne is one of the more famous traditional or "trad" routes in the area, and has long sections between protection. Eldorado Canyon, located on the Front Range south of Boulder, and its steep, difficult sandstone cliffs attract climbers from around the country and the world, making it one of the most popular climbing areas in Colorado.

Beautiful view of Great Wall looking east near Simatai. The wall continuing up over steep inclines on mountain ridges in distance.

A climber on a ladder of the Klettersteig to the top of the Schwarzhorn, a mountain above Grindelwald in the Swiss Alps.

A man climbs a wall of ice in Whistler, British Columbia, Canada, Whistler, British Columbia, Canada

Mountaineers Are At The Base Of A Steep Wall On Denali, Alaska

Mother and daughter female tourists standing in front of the Great Pyramid of Giza, Giza, Egypt

Fjadrargljufur is a magnificent and massive canyon, about 100 meters deep and about two kilometres long. The canyon has sheer walls; Skaftarhreppur, Southern Region, Iceland

Fjadrargljufur is a magnificent and massive canyon, about 100 meters deep and about two kilometres long. The canyon has sheer walls; Skaftarhreppur, Southern Region, Iceland

Steps leading to ruined stone temple towers, East Mebon, Angkor Wat, Siem Reap, Siem Reap Province, Cambodia

Kuelap Fortress ruins Chachapoyas culture also known as the Cloud Forest People, Site discovered 1843, Steep narrow pathway between stone walls, Chachapoyas, Amazonas, Peru

Bhutan, Thimpu, Gold painted carving of Guru Rimpoche on rock wall.