40,270 articles
Obilonna
Obilonna (also Obilunnum, Obilinnum) is a Roman road station on the Tabula Peutingeriana in the Graian Alps, Savoie, France, usually identified with La Bâthie or Conflans on the Vienne to Darantasia road.
Obilukha Corona
Obilukha Corona is a 220-km-diameter corona on Venus at 81.5°S, 19°E in quadrangle V-62, named in 1997 after an East Slavic crop protection deity, per the USGS planetary nomenclature gazetteer.
Oblast
An oblast (Russian: область) is a first-level administrative division in Russia and Ukraine and other post-Soviet states, typically translated as region; Russia's oblasts are equal subjects of the Federation, and Ukraine has 24.
Oblast Pleven
Oblast Pleven (Област Плевен), a province of northern Bulgaria, NUTS 3 code BG314, capital Pleven; 212,890 people (2025), 4,653 sq km, 11 municipalities, Danube border, site of the 1877 Siege of Pleven.
Oblast Stara Zagora
Oblast Stara Zagora (Област Стара Загора), a Bulgarian district (NUTS3 BG344) named after the city of Stara Zagora; 286,722 residents on 31.12.2025, 11 municipalities, 5,148 sq km, fifth most populous district, highest 2025 regional poverty rate.
Oblast Veliko Tarnovo
Oblast Veliko Tarnovo, also known as Veliko Tarnovo Province, is one of Bulgaria's 28 districts in Central Northern Bulgaria, centered on the city of Veliko Tarnovo.
Oblasts of Russia
An oblast (область) is the most common type of federal subject in Russia, where 46 oblasts function as province-level regions, each with a governor and legislature.
Oblasts of Ukraine
Oblasts of Ukraine: the 24 first-level regions named in Article 133 of the 1996 Constitution, alongside Crimea and Kyiv and Sevastopol; created from 1932, reformed in 2020 (136 raions, 1,469 hromadas), governed by elected councils and presidentially appointed governors.
Oblin
Oblin (site 5, Gmina Maciejowice, Poland): a fully excavated Przeworsk culture cremation cemetery on the Vistula, dug 1986–1995 by Katarzyna Czarnecka; about 314 graves from the 2nd century BC to the 2nd century AD, distinct from the eastern Przeworsk zone.
Obruchev (lunar crater)
Obruchev is a 72.23-km-wide impact crater on the Moon's far side south of Mare Ingenii, Nectarian in age, named for Soviet geologist Vladimir Afanasievich Obruchev (1863-1956) and IAU-approved in 1970.
Obshtina Burgas
Obshtina Burgas (Община Бургас), Burgas Municipality, is a Bulgarian municipality in Burgas Province on the Black Sea, centered on the city of Burgas (198,035 people in 2022), led by Mayor Dimitar Nikolov since 2007, with 15 settlements and the Lukoil Neftochim refinery anchoring its economy.
Obshtina Plovdiv
Obshtina Plovdiv (Община Пловдив), Plovdiv Municipality, is a second-order administrative division in southern Bulgaria around the city of Plovdiv; 333,994 residents as of 31.12.2025, six districts, second largest Bulgarian municipality after Stolichna.
Obshtina Varna
Obshtina Varna (Община Варна) is Bulgaria's third-largest municipality, in Varna Province, centered on the city of Varna. 331,260 residents (2025), five urban quarters, five villages, maritime and tourism economy.
Obtawaing Biosphere Reserve
Obtawaing Biosphere Reserve (Obtawaing Biosphere Region), a UNESCO Man and the Biosphere site in Northern Michigan designated in 1979 as the University of Michigan Biological Station reserve, expanded and renamed in 2021, spanning Lakes Huron, Michigan, and Superior.
Obuase
Obuase (modern spelling Obuasi) is a gold-mining city in Ghana's Ashanti Region, seat of the Obuasi Municipal Assembly; mining began with the 1897 Ashanti Goldfields concession, and the 2021 census counted 104,297 residents.
Obukhiv Raion
Obukhiv Raion (Обухівський район), a district of Kyiv Oblast, Ukraine, centered on Obukhiv; created 17 July 2020 by resolution 807-IX, covering 3,635.3 km² with 229,518 people in 9 hromadas and 200 localities.
Ocala, Florida
Ocala, Florida: county seat and largest city of Marion County in north-central Florida, the "Horse Capital of the World" with about 600 thoroughbred farms, Silver Springs glass-bottom boats, and the fastest-growing U.S. metro in 2025.
Ocaña, Norte de Santander
Ocaña is a city and municipality in the Colombian department of Norte de Santander, founded in 1570 and known for hosting the Gran Convención of 1828.
Occaraba
Occaraba, an ancient town of Roman Syria on the Tabula Peutingeriana, also Orarabon, Ovvariba, Akoraba; identified with 'Agerbat/Uqayribat, Barrington Atlas 68 D3, Pleiades 668322, dated Roman/Late Antique.
Occator (crater on Ceres)
Occator is a 92-km-wide, 4-km-deep impact crater on dwarf planet Ceres, centered at 19.82°N, 239.33°E, holding Ceres' brightest areas, Cerealia Facula and Vinalia Faculae: young sodium carbonate salt deposits from upwelling brines.
Occidental Mindoro
Occidental Mindoro, a Philippine province in MIMAROPA occupying western Mindoro Island, capital Mamburao, created 1950 by Republic Act No. 505; 11 municipalities, land area 5,879.85 sq km, population 511,417 (2024 census).
Occitania
Occitania (Occitània) is the cultural-historical region of southern France, with edges in Spain and Italy, where Occitan and its six dialects, from Gascon to Provençal, are traditionally spoken; medieval troubadour land, now an endangered-language revival region.
Occitania (administrative region)
Occitania (Occitanie), French administrative region created 1 January 2016 from Languedoc-Roussillon and Midi-Pyrénées, capital Toulouse; 13 departments, 72,724 km², about 6.2 million people, France's fastest-growing metropolitan region after Corsica.
Occupation of Mongolia
Occupation of Mongolia covers the 1919–1921 Chinese reoccupation of Outer Mongolia, the 1921 White Russian and Soviet takeovers of Urga, and Japan's occupation of Inner Mongolia through Mengjiang (1936–1945) under Prince Demchugdongrub.
Occupation of the Baltic states
Occupation of the Baltic states: successive Soviet (1940-41, 1944-91) and Nazi German (1941-44/45) occupations and annexations of Estonia, Latvia, and Lithuania, following the Molotov-Ribbentrop Pact, with mass deportations, staged 1940 elections, US non-recognition, and restored independence in 1991.
Ocean
The ocean is the interconnected salt-water body covering about 70% of Earth's surface, holding 97% of its water, absorbing roughly 30% of CO2 emissions and 93% of excess heat, and governed largely under UNCLOS.
Ocean Beach, San Diego
Ocean Beach (OB) is a coastal San Diego neighborhood on Point Loma, known for its 1966 concrete pier, Dog Beach, Newport Avenue's independent shops, a 30-foot height limit, and a $170–190 million pier replacement project.
Ocean Beach, San Francisco
Ocean Beach is San Francisco's roughly five-mile Pacific shoreline south of the Cliff House, backed by the Great Highway and O'Shaughnessy seawall, an erosion hot spot studied by USGS, and fronted since 2025 by the car-free Sunset Dunes park.
Ocean City, Maryland
Ocean City, Maryland is a barrier-island resort town in Worcester County, between the Atlantic and Sinepuxent Bay. Founded around the 1875 Atlantic Hotel, incorporated 1880, population 6,844 (2020), Maryland's primary seaside resort.
Ocean County, New Jersey
Ocean County, New Jersey: county formed February 15, 1850 from Monmouth County lands south of the Manasquan River; county seat Toms River; 33 municipalities, 638 square miles, 45-mile Atlantic coast; population 637,229 (2020).