Nurnus Castle

Armenia

Nørreris Castle

Denmark

Nørtorp

Denmark

Odals Verk manor

Norway

Oglan Castle

Azerbaijan

Oguz Castle

Azerbaijan

Opila Fortress

North Macedonia

Orašac Fort

Bosnia and Herzegovina

Oraše Fortress

North Macedonia

Orosz Mátyás Castle

Hungary

Oroszlánkő Castle (Csáki Castle)

Hungary

Oslo kongsgård Kastell

Norway

Ruin

Oudeberg Castle

Belgium

Oudenwal Castle

Belgium

Overud gård

Norway

Owlad castle

Iran

Owltan castle

Iran

Pabargad

India

Pahlavan Badi castle

Iran

Palace: Generally newer building

Denmark

Palangan castle

Iran

Palaytha Fort

India

Palazzo dei Conti di Celano

Italy

Palgad

India

Pangna Fort

India

Panj Berar Murmuri castle

Iran

Pap-hegy Castle

Hungary

Paqala Hezarani castle

Iran

Pargadh

India

Parola Fort

India

Parvizeh Evaz castle

Iran

Pemzashen Castle

Armenia

Peredmirka Castle

Ukraine

Pesočani Fortress

North Macedonia

Petke Castle

Hungary

Pettah of Ahmednagar

India