Doraha Fort, India

Llama at Machu Picchu

Overgrown ruins of Lekarti Monastery, Azerbaijan

Ruined medieval tower in Perperikon, Bulgaria

Dunseverick Castle, Antrim, Ireland

Kells Priory in Kilkenny County, Ireland

Remains of the small Roman fort at Qasr El Benia, Tunisia

Ruins of Seleucia, Turkiye

Ottoman-era fort near El Haouaria, Tunisia

Tongoni Ruins, Tanzania

Slightly off-topic - a new AskHistorians comm has opened, for those interested!

Watchtower of Sydoriv Castle, Ukraine

Bayon, Angkor, Cambodia

Necropolis in Khirbet Kurkush, West Bank, Palestine

The crypt under Notre Dame, Paris [OC]

Shahbulag Mosque, Azerbaijan

Pirita Convent, Estonia

La Venta Pyramid, Mexico

Jarlshof, Scotland

Broch of Mousa, Scotland

Graeco-Roman ruins in Butrint, Albania

The Colony, Bennachie, Scotland [MIC]

Huntly Castle, Scotland [MIC]

Citadel of Al-Rahba, Syria

Buchanan Castle, Scotland

Dunure Castle, Scotland

Kildrummy Castle, Scotland

Tomri Sahib Temple, Pakistan

Snow-covered remains of Fredriksholm Fortress, Norway

Remains of Akagi Castle, Japan

Salgo Castle, Hungary

Phu Pek, Thailand

Watermill remains in Yaoli, China

Hindu shrine in Amarkantak, Madhya Pradesh, India

Stones carved into a sacrificial site during the Roman Empire, Panoias Sanctuary, Portugal

Ruins of the Islamic university of Shah-e Mashhad, Afghanistan

Excavated Ancient Roman street in Pompeii, Italy

Ruins of the church at Katarínka, Slovakia

Tap o' Noth Hillfort, Scotland

Dunalastair House, Scotland

Lanark District Asylum, Scotland

Lennox Castle Hospital, Scotland

Dunnotar Castle, Scotland [MIC]

New Slains Castle, Scotland

Dunnideer Castle, Scotland [MIC]

Carrbridge Packhorse Bridge, Scotland

Remains of Somogyvar Abbey, Hungary

Interior of the Dolmen of Menga, Spain

Monastery of Saint Elijah, Iraq, 2005