Humberstone Saltpeter Works, UNESCO World Heritage Site, northern Atacama, Chile, South America

View of Aqueduct from the Ottoman era and Kavala Fortress, Dimos Kavalas, Eastern Macedonia and Thrace, Gulf of Thasos, Gulf of Kavala, Thracian Sea, Greece, Europe

The Byzantine era fortress on Guvercin Ada (Pigeon Island), looking into the Aegean Sea, in the harbour of Kusadasi, Turkey, Asia Minor, Eurasia

The Byzantine-era fortress, illuminated at dusk, on Guvercin Ada (Pigeon Island), on the Aegean coast, in Kusadasi, Turkey, Asia Minor, Eurasia

Soviet-era nuclear bunker, central Tirana, Albania, Europe

Aerial view of Venetian Fortezza Castle, Rethymno, Crete, Greek Islands, Greece, Europe

View of Aqueduct from the Ottoman era, Dimos Kavalas, Eastern Macedonia and Thrace, Gulf of Thasos, Gulf of Kavala, Thracian Sea, Greece, Europe

Den Gamle By (The Old Town), open air town museum of 75 historical buildings from 20 townships in all parts of the country, originally erected between 17th and 20th centuries, Aarhus, Jutland Peninsula, Denmark, Europe

Ruined bombed house in the old port town of Massawa, Eritrea, Africa

Souvenir badges of the Soviet Republic communist era, Moscow, Russia, Europe

Angkor era ruins of Wat Nokor, Kampong Cham, Cambodia, Indochina, Southeast Asia, Asia

Angkor era ruins of Wat Nokor, Kampong Cham, Cambodia, Indochina, Southeast Asia, Asia

Poster from Late Mao era, China, Asia

Ruins of the Roman-era Imperial Palace of Galerius on Navarinou square in Thessaloniki, Greece, Europe

Get together of the community of interests for historical performance of the 18th century, moated castle Linn, Krefeld, NRW, Germany

Men wearing Prussian infantry uniform, members of the community of interests for historical performance of the 18th century, moated castle Linn, Krefeld, NRW, Germany

Clenched fist, torchbearer, monumental stone sculpture from the Nazi era, former NS-Ordensburg Vogelsang, International Place in Eifel National Park, Schleiden-Gemuend, North Rhine-Westphalia, Germany, Europe

"Stumbling blocks", reminiscent stones to expelled and deported Jews during the Nazi era in Hamburg-Hoheluft

High angle view of El Morro Fort, San Juan, Puerto Rico

High angle view of El Morro Fort, San Juan, Puerto Rico

Communist era statues are on permanent display in the Statue Park outside Budapest, Hungary, Europe

Communist era statues are on permanent display in the Statue Park outside Budapest, Hungary, Europe

Communist era statues are on permanent display in the Statue Park outside Budapest, Hungary, Europe