Ooty (short for Udhagamandalam) is a resort town in the Western Ghats mountains, in southern India's Tamil Nadu state. Founded as a British Raj summer resort, it retains a working steam railway line.

Opatija is a Croatian coastal town on the Adriatic Sea. A fashionable resort in the 19th century, it's dotted with Habsburg-era villas. The Lungomare is a promenade that snakes along the coastline, offering views of the town and neighbouring islands.

Open Space Visitor Center is the place to learn about the 29,000 acres within the Open Space system.

The Orange River is a river in Southern Africa. It is the longest river within the borders of Lesotho and the Orange River Basin extends extensively into South Africa, Namibia, and Botswana to the north.

Ordesa y Monte Perdido National Park is an IUCN Category II National Park situated in the Pyrenees

Oriente, region of eastern Ecuador, comprising the eastern slopes of the Ecuadorian Andes and the lowland areas of rainforest in the Amazon basin. It is bounded on the north by San Miguel and Putumayo rivers and on the east and south by Peru.

Osijek is the fourth largest city in Croatia with a population of 108,048 in 2011. It is the largest city and the economic and cultural centre of the eastern Croatian region of Slavonia, as well as the administrative centre of Osijek-Baranja County.

Osorno is a city in south-central Chile, on the Rahue River. The 18th-century Reina Luisa Fort stands beside the river. The Museo Histórico Municipal has exhibits on the Mapuche culture and the 19th-century German settlers who built nearby mansions.

Otago Harbour is the natural harbour of Dunedin, New Zealand, consisting of a long, much-indented stretch of generally navigable water separating the Otago Peninsula from the mainland. They join at its southwest end, 21 km from the harbour mouth.

Otavalo is a town in the Andean highlands in the Imbabura province of northern Ecuador. It’s surrounded by volcanoes including the Imbabura Volcano.