Poznań is now Poland's fifth largest city. It is the historical capital of the Wielkopolska ("Greater Poland") region, and is currently the administrative capital of the province called Greater Poland Voivodeship.
In 1138, by the testament of Bolesław III, Poland was divided into separate duchies under the late king's sons, and Poznań and its surroundings became the domain of Mieszko III the Old, the first of the Dukes of Greater Poland. This period of fragmentation lasted until 1320. Duchies frequently changed hands; control of Poznań, Gniezno and Kalisz sometimes lay with a single duke, but at other times these constituted separate duchies.
In reunited Poland, and later in the Polish–Lithuanian Commonwealth, Poznań was the seat of a voivodeship. The city's importance began to grow in the Jagiellonian period, due to its position on trading routes from Lithuania and Ruthenia to western Europe. It would become a major centre for the fur trade by the late 16th century. Suburban settlements developed around the city walls, on the river islands and on the right bank, with some (Ostrów Tumski, Śródka, Chwaliszewo, Ostrówek) obtaining their own town charters. However the city's development was hampered by regular major fires and floods. On 2 May 1536 a blaze destroyed 175 buildings, including the castle, the town hall, the monastery and the suburban settlement called St. Martin.
In the second half of the 17th century and most of the eighteenth, Poznań was severely affected by a series of wars (and attendant military occupations, lootings and destruction) – the Second and Third Northern Wars, the War of the Polish Succession, the Seven Years' War and the Bar Confederation rebellion. It was also hit by frequent outbreaks of plague, and by floods, particularly that of 1736, which destroyed most of the suburban buildings. The population of the conurbation declined (from 20,000 around 1600 to 6,000 around 1730), and Bambergian and Dutch settlers (Bambrzy and Olędrzy) were brought in to rebuild the devastated suburbs. In 1778 a "Committee of Good Order" (Komisja Dobrego Porządku) was established in the city, which oversaw rebuilding efforts and reorganized the city's administration. However in 1793, in the Second Partition of Poland, Poznań, came under the control of the Kingdom of Prussia, becoming part of (and initially the seat of) the province of South Prussia.
In the Greater Poland Uprising of 1806, Polish soldiers and civilian volunteers assisted the efforts of Napoleon by driving out Prussian forces from the region. The city became a part of the Duchy of Warsaw in 1807, and was the seat of Poznań Department - a unit of administrative division and local government. However in 1815, following the Congress of Vienna, the region was returned to Prussia, and Poznań became the capital of the semi-autonomous Grand Duchy of Posen.
- The Archcathedral Basilica of St. Peter and St. Paul is one of the oldest churches in Poland and the oldest Polish cathedral, dating from the 10th century. It stands on the island of Ostrów Tumski north-east of the city centre. The cathedral was originally built in the second half of the 10th century within the fortified settlement (gród) of Poznań. This was one of the main political centres in the early Polish state, and included a ducal palace (excavated by archaeologists since 1999, beneath the Church of the Virgin Mary which stands in front of the cathedral). Saint Peter became the patron of the church because, as the first cathedral in the country, it had the right to have the same patron as St. Peter's Basilica in the Vatican. The first church survived for about seventy years, until the period of the pagan reaction and the raid of the Bohemian duke Bretislav I (1034–1038). In the 14th and 15th centuries, the church was rebuilt in the Gothic style. At that time, a crown of chapels was added. A fire in 1622 did such serious damage that the cathedral needed a complete renovation, which was carried out in the Baroque style. Another major fire broke out in 1772 and the church was rebuilt in the Neo-Classical style. In 1821, Pope Pius VII raised the cathedral to the status of a Metropolitan Archcathedral and added the second patron - Saint Paul. The last of the great fires occurred on 15 February 1945, during the liberation of the city from the Germans. The damage was serious enough that the conservators decided to return to the Gothic style, using as a base medieval relics revealed by the fire. The cathedral was reopened on 29 June 1956. In 1962, Pope John XXIII gave the church the title of minor basilica.
- Grand Theatre, Poznań is a neoclassical opera house named after famous Polish composer Stanisław Moniuszko. Designed by German architect Max Littmann, and inaugurated in 1910 with The Magic Flute (Wolfgang Amadeus Mozart), is a main opera stage in Greater Poland Voivodeship currently directed by Michał Znaniecki. Its season runs from mid-September to mid-June and the company mounts an annual "Festival Verdi" in October and "E. T. A. Hoffmann Festival" in April, often with special guests.
- Poznań Town Hall or Ratusz is located in the Old Market Square (Stary Rynek) in the centre of the Old Town neighbourhood. It served as the city's administrative building until 1939, and now houses a museum. The town hall was originally built in the late 13th century following the founding of the medieval city in 1253; it was rebuilt in roughly its present-day form, in mannerist style, with an ornate loggia, by Giovanni Battista di Quadro in 1550–1560. The display of mechanical fighting goats, played out daily at noon above the clock on the front wall of the building, is one of the city's main tourist attractions.
- The Museum of Poznan Uprising 1956 Placed in the interiors of Emperor's Castle shows exhibits connected with the Poznan workers' protest against the communist system in June 1956. On the exhibition there are photos of attendants and their personal belongings, as well as historical sources about the anticommunist opposition between 1945-1989. An interesting thing is a reconstructed tram, used by protestants as a barricade.
- The Imperial Castle popularly called Zamek, is a palace in Poznań. It was constructed in 1910 by Franz Schwechten for William II, German Emperor, with significant input from William himself. Since its completion, the building has housed government offices of Germany (to 1918 and during the Second World War) and Poland (1918–1939, 1945–present). During fighting in 1945, the castle was a temporary camp for German POWs, and was later used as a barracks by the Polish People's Army. During this period, the communist government considered the demolition of the castle as a symbol of the German occupation and bourgeois style. Due to a lack of funds, only some of the German symbols were removed and the upper part of damaged tower was demolished.
During the war, the city hall and the seat of the town authorities was destroyed. The castle was renamed to "New City Hall" (Nowy Ratusz), and later transformed into a centre of culture. On 6 June 1979 the castle was declared a historical monument under protection of law. Today, the Throne Room is used as a cinema room; other apartments contain art galleries, a puppet theater, pubs, music clubs and restaurants. The courtyard is often a place of concerts and outdoor movie performances during summer. The second floor is still empty and has not been renovated. The square in front of the building is the main venue for the St. Martin's Day parade and celebrations held in Poznań annually on November 11.