It lies 15 km (9 mi) from the border with Poland, at the confluences of four rivers: Oder, Opava, Ostravice and Lučina.

The wider conurbation – which also includes the towns of Bohumín, Havířov, Karviná, Orlová, Petřvald and Rychvald – is home to about 500,000 people,[2] making it the largest urban area in the Czech Republic apart from the capital Prague.

During the 20th century it was known as the "steel heart" of Czechoslovakia thanks to its status as a coal-mining and metallurgical centre, but since the Velvet Revolution (the fall of communism in 1989) it has undergone radical and far-reaching changes to its economic base.

[5] In addition, Ostrava is divided into 37 municipal parts, 18 of them identically defined as boroughs (in brackets population according to the 2021 census):[6] The city's coat of arms features a blue shield with a rearing silver horse standing on a green lawn.

There is also a legend which tells of a siege of Ostrava during which the besieged townspeople released unbridled horses to run in circles around the town.

[10] A turning point in Ostrava's history came in 1763 with the discovery of extensive deposits of high-quality bituminous coal on the Silesian bank of the Ostravice River.

In 1828, the owner of the local estates, Rudolf Jan, the archbishop of Olomouc, established an ironworks, which was named after him as the Rudolfshütte.

Initially, the new housing projects were on a relatively-small scale focusing on the Poruba district and featuring architecture in the Socialist realism style.

Later, however, the authorities built larger-scale developments of prefabricated apartment blocks in Poruba and created a series of satellite estates to the south of the city (Ostrava-Jih).

The 1990s brought a rapid decline in the city's traditional industrial sectors: iron, steel, chemicals and coal-mining.

The last coal was mined on 30 June 1994, which was accompanied by major investments to rectify ecological damage done by decades of heavy industry.

Ostrava became an important tourist centre that offered easy access to the nearby Hrubý Jeseník and Moravian-Silesian Beskids mountains.

They include the Polanský Forest and the Polanská Meadows, both of which form part of the Poodří (Oder Basin) nature reserve.

It lies mostly in the Ostrava Basin lowland, only the southwestern part of the municipal territory extends into the Moravian Gate.

It differs from most neighbouring regions by the high concentration of industry, dense population and the geographical conditions of the Ostrava Basin.

Ostrava has an oceanic (Köppen: Cfb) or humid continental (Dfb) climate, according with the isotherm 0 °C/-3 °C, the second most common in Europe (the average temperature in month most cold is −1 °C (30 °F)).

Ostrava is the transport and logistics hub of the north-eastern part of the Czech Republic, located close to the borders with Slovakia and Poland, and with an airport and highway connection nearby.

New tram lines were built mainly to the south and east of the city centre, where they would not have to cross the narrow-gauge railways linking Ostrava with Karviná and Bohumín.

The main line linking Ostrava with Olomouc, Pardubice and Prague is served by three railway companies: České dráhy, RegioJet and LEO Express.

Ostrava's high concentration of heavy industry created various environmental problems in the city, particularly in relation to air quality.

Measurements performed by the Czech Hydrometeorological Institute show that levels of atmospheric benzopyrene and dust particles are among the highest in the country.

In 2015 ArcelorMittal, then one of the biggest polluters in the region, implemented 13 major ecological investment projects worth CZK 3 billion.

One of the most pressing environmental problems currently facing the city concerns the oil lagoons at the site of the former Ostramo chemical plant.

The most notable structures are theatres, banks, department stores and other public buildings dating from the turn of the 20th century, at the time of Ostrava's greatest boom.

To the west are a series of grand, imposing bank buildings and the Elektra Palace on Nádražní Street, while to the north is the New City Hall with its landmark viewing tower, overlooking the large open space of Prokeš Square.

Ostrava's central district contains works by architects including Karel Kotas, Josef Gočár, Ernst Korner and Alexander Graf.

Poruba is a large district of Ostrava in the western part of the conurbation, noted for its distinctive 1950s Socialist realist architecture.

Inspired by the grandiose buildings of Soviet cities, Poruba also incorporates historical pastiche features drawing on ancient, Renaissance and Classicist models.

The influx of workers led the company to build housing for its employees, plus civic amenities, a town hall and a church.

Ostrava's Regional Court is based in a historic building on the Ostravice embankment (Havlíčkovo nábřeží) in the city centre.