The illuminated city walls of Dubrovnik at night, UNESCO World Heritage Site, Dubrovnik, Croatia, Europe

The main square (Trg Svetog Stjepana) of Hvar Town with view to the Spanish Fortress in the background at first sunlight, Hvar, Croatia, Europe

Colourful display of flowers at the Festival of the Patios, Cordoba, Andalucia, Spain, Europe

Murals in the royal palace complex depicting scenes from the Ramayana, Phnom Penh, Cambodia, Indochina, Southeast Asia, Asia

Villa Balbiano, Ossuccio, Lake Como, Lombardy, Italian Lakes, Italy, Europe

Kalmar Castle, Kalmar, Sweden, Scandinavia, Europe

The entrance tower of Abbey of Santa Maria in Sylvis, Sesto al Reghena, Pordenone, Friuli Venezia Giulia, Italy, Europe

Rampart Walls and Towers, Saviour Monastery of St. Euthymius, UNESCO World Heritage Site, Suzdal, Vladimir Oblast, Russia, Europe

Taxi Brousse Bus stop and a cyclo-pousse in Morondava, Western Madagascar, Africa

Gateway entrance of the Medina shopping and restaurant complex, Yasmine Hammamet, Cap Bon, Tunisia, North Africa, Africa

Faces of historic figures, Independence monument in Barrio San Roman, Campeche city, Campeche State, Mexico, North America

Templo Mayor, archaeological site of Aztec capital city of Tenochtitlan, view to Casa del Marques de Prado, Centro Historico, UNESCO World Heritage Site, Mexico City, Mexico, North America Prado Alegre

Palais Claudio Bravo, Taroudant, Sous Valley, Morocco, North Africa, Africa

Mount Popa, home of the Mahagiri Nats (spirits), Myanmar (Burma)

Listvianka, Lake Baikal, Siberia, Russia

Yorkshire Dales, Yorkshire, England, UK, Europe

Dunrobin Castle and grounds, near Golspie, Sutherland, Highlands Region, Scotland, UK, Europe

Sun and fields, Robe, South Australia, Australia, Pacific

View across River Rhone to bridge and Papal Palace, Avignon, UNESCO World Heritage Site, Provence, France, Europe

View of Jaisalmer and old surrounding walls, western Rajasthan, Rajasthan state, India, Asia

Isola Bella, Boromean Islands, Lake Maggiore, Italian Lakes, Piemonte (Piedmont), Italy, Europe

Fasiladas' Palace, The Royal Enclosure, Gonder, Ethiopia, Nortern Ethiopia, Africa

Cellular Jail, Port Blair, Andaman Islands, India, Asia

Bicycle cruises past homes, Iquitos, Peru, South America

A colourful house on Burano, Venice, UNESCO World Heritage Site, Veneto, Italy, Europe

Farm gate and overcast skies near Malham, Yorkshire Dales National Park, Yorkshire, England, United Kingdom, Europe

A sphinx stands in front of Luxor Temple, Luxor, Thebes, UNESCO World Heritage Site, Egypt, North Africa, Africa

Che Guevara Monument and Mausoleum, Santa Clara, Villa Clara Province, Cuba, West Indies, Caribbean, Central America

Signs of the Civil War in Sant Felip Neri Square, Gothic Quarter, Barcelona, Catalonia, Spain, Europe

Trulli, Alberobello, UNESCO World Heritage Site, Puglia, Italy, Europe

Colourful wall paintings in the Church of Elijah the Prophet in Yaroslavl, UNESCO World Heritage Site, Golden Ring, Russia, Europe

Entrance to Las Pozas, the pools, surrealist sculpture garden and architecture created by Edward James an eccentric English aristocrat, Xilitla, San Luis Potosi state, Mexico, North America

Cowboy Hats, Patzcuaro, Michoacan State, Mexico, North America

Statue of George Washington standing outside the Federal Hall, Wall Street, New York City, New York, United States of America, North America

Derelict barn in wheat field, Northern Wyoming, United States of America, North America

The Citadel, Erbil, Kurdistan, Iraq, Middle East

Venetian port of Rethymnon, Crete, Greek Islands, Greece, Europe

Security wall in Bethany, Israel, Middle East

Santiago pilgrims' guest house, St.-Jean-Pied-de-Port, Pyrenees Atlantique, France, Europe

Gubeikou to Jinshanling section of the Great Wall of China, UNESCO World Heritage Site, Miyun County, Beijing Municipality, China, Asia

Stadium of Domitian on Palatine Hill, UNESCO World Heritage Site, Rome, Lazio, Italy, Europe

Walls of China, a series of Lunettes in the Mungo National Park, part of the Willandra Lakes Region, UNESCO World Heritage Site, Victoria, Australia, Pacific

Mount Orgueil Castle, overlooking Grouville Bay in Gorey, Jersey, Channel Islands, United Kingdom, Europe

Perast harbour with cafes and boats moored up, Bay of Kotor, UNESCO World Heritage Site, Montenegro, Europe

Muralhas de Sao Sebastiao (walls of St. Sebastian), fortress constructed to defend the bay of Porto Paim, and the marina, Horta, island of Faial, with Pico mountain on the island of Pico in the distance, Azores, Portugal, Atlantic, Europe

The Arab Puerta de Almodovar and the mediaeval wall, Cordoba, Andalucia, Spain, Europe

Frescoes at Rila Monastery, UNESCO World Heritage Site, Bulgaria, Europe

Inside the walls of the restored fort of Nakhal in the Western Hajar mountains of Oman, Middle East

Temple of the South, Edzna, Mayan archaeological site, Campeche, Mexico, North America

Templo Redondo (Round Temple), Mayapan, Mayan archaeological site, Yucatan, Mexico, North America

Cannons on ramparts of citadel castle Il-Kastell, Victoria Rabat, Gozo, Malta, Mediterranean, Europe

Empty road leading through stone gateways under a cloudy sky, North Yorkshire, England, United Kingdom, Europe

Garden of historic castle in medieval village of Marvao, Portalegre district, Alto Alentejo, Portugal, Europe

Monasterio de Yuste, Monastery at Cuacos de Yuste, La Vera, Extremadura, Spain, Europe

Ancient frescoes, Sigiriya, UNESCO World Heritage Site, North Central Province, Sri Lanka, Asia

Chaco Culture National Historic Park, World Heritage Site, Pueblo Bonito, kiva (foreground), UNESCO World Heritage Site, New Mexico, United States of America, North America

St. Peter with the key, Cloister of Saint Sauveur cathedral, Aix en Provence, Bouches du Rhone, Provence, France, Europe

Monument of Agonothetes (Bouleuterion), Roman 2nd century AD, Apollonia Archaeological Park, Pojan, Albania, Europe

View of whitewashed buildings on mountainside, village of Dhermi, Albania, Europe

Detail of mural depicting Life of the Buddha, Wat Phnom, Phnom Penh, Cambodia, Indochina, Southeast Asia, Asia

Historic buildings on the Grand Harbour waterfront in Valletta, Malta, Mediterranean, Europe

Commissioner's House and part of the old fort wall at the Royal Naval Dockyard, Bermuda, Central America

The Venetian era harbour walls and lighthouse at the Mediterranean port of Chania (Canea), Crete, Greek Islands, Greece, Europe

Saadian Tombs, Medina, Marrakesh, Morocco, North Africa, Africa

Walls and towers at night of the Aljaferia Palace, dating from the 11th century, Saragossa (Zaragoza), Aragon, Spain, Europe

City walls and Ramparts, Avignon, Provence, France, Europe

East Side Gallery, Berlin Wall Museum, Berlin, Germany, Europe

The 16th century Amber Fort complex just outside Jaipur, Rajasthan, India, Asia

Olympic Port, Golden Whale, Barcelona, Catalonia, Spain, Europe

Citadel (Tower of David), Old City Walls, UNESCO World Heritage Site, Jerusalem, Israel, Middle East

A pagoda in the grounds of the Imperial Citadel, Hue, UNESCO World Heritage Site, Vietnam, Indochina, Southeast Asia, Asia

View of the River Seine from the Roche Guyon Castle, Normandy, France, Europe

Wooden wine barels in sandstone wine cellar, Novy Saldorf, Brnensko, Czech Republic, Europe

Bender fortress in Bender, Republic of Transnistria, Moldova, Europe

Mosaic icon at Monastery of St. John at Chora, UNESCO World Heritage Site, Patmos, Dodecanese, Greek Islands, Greece, Europe

The great Rupe Magna in Grosio, on which ancient peoples have left their testimony. Valtellina, Lombardy, Italy, Europe

Waves crash against the harbour wall at Porthcawl, Bridgend, Wales, United Kingdom, Europe

Wells Cathedral reflected in the Bishop's Palace moat, Wells, Somerset, England, United Kingdom, Europe

Monreale Cathedral, Palermo, Sicily, Italy, Europe

Remains of the old city walls outside the Museum of the Revolution, Havana, Cuba, West Indies, Central America

Changing of the Guard at the Tomb of the Unknown Soldier in Syntagma Square with the Old Royal Palace, Athens, Greece, Europe

Skyline, Panama City, Panama, Central America

Eketorp Fortress, Oland, Sweden, Scandinavia, Europe

Wall mosaics in the Founders of the Bulgarian State Monument (Monument to 1300 Years of Bulgaria), Shumen, Bulgaria, Europe

Tourists walks on the ancient walls of Cagliari, Cagliari province, Sardinia, Italy, Mediterranean, Europe

Xi'an City Wall, Shaanxi Province, China, Asia

View from the public garden, Parco Duca di Cesaro, Taormina, Sicily, Italy, Europe

External Frescoes, Sucevita Monastery, 1585, UNESCO World Heritage Site, Sucevita, Suceava County, Romania, Europe

Old city walls, entrance to historic castle site, Cuenca, Castille La Mancha, Spain, Europe

Old stone wall with the Peak of Shutlingsloe, near Wildboarclough, Peak District National Park, Cheshire, England, United Kingdom, Europe

Winter view of Hen Cloud with snow, The Roaches, Peak District, Staffordshire, England, United Kingdom, Europe

Tourists walking over moat bridge through entrance gateway of medieval city of Mdina, Malta, Mediterranean, Europe

Spanish colonial fortification, Fort de San Felipe, Bacalar, Quintana Roo, Yucatan Peninsula, Mexico, North America

Archaeological site of Castro de Santa Trega, Castro Culture settlement, A Guarda, Pontevedra Province, Galicia, Spain, Europe

Fishing net floats, Oak Bluffs, Martha's Vineyard, Massachusetts, USA

The beach, Estoril,Costa de Lisboa, Portugal, Europe

The Matterhorn towering above green pastures and wooden huts, Zermatt, Valais (Wallis), Swiss Alps, Switzerland, Europe

Outer walls of Sacsayhuaman Inca Fortress, Cuzco, Peru, South America

Medieval town walls and spire of St. Olav's church at dusk, Tallinn, Estonia, Baltic States, Europe

Scalloway Castle, Shetlands, Scotland, UK, Europe