Bielefeld is a district-free town in the Regierungsbezirk Detmold in the north-east of North Rhine-Westphalia, Germany. It is located at 52°01′00″N, 08°31′00″E on both the western and eastern slopes of the Teutoburg Forest. With its population of 326,000, it is the biggest city of the Ostwestfalen-Lippe Region. The current mayor is Eberhard David.
The name Bielefeld is derived from the old name bileveld, which means "hilly field". The city is situated below a pass separating the Northern and Southern Teutoburg Forest. The centre of Bielefeld is situated on the eastern side of the Teutoburg Forest, but the modern city incorporates boroughs on the opposite side and on the hilltops.

Sparrenburg Castle is the most famous landmark. It was built between 1240 and 1250 by Count Ludwig von Ravensberg. The 37 m (121 ft) high tower and the catacombs of the castle are open to the public.
The Old City Hall (Altes Rathaus) was built in 1904 and still serves the same function. On its facade on can find various architectural styles, including elements of the Gothic style and of the Renaissance. Though the mayor still holds office in the Old City Hall, the most of the city's administration is housed in the adjacent New City Hall (Neues Rathaus).
The City Theater (Stadttheater) is part of the same architectural ensemble as the Old City Hall, also built in 1904. It has a notable Jugendstil facade. It is Bielefeld's largest theater.
The oldest city church is Altstädter Nicolaikirche. It is a Gothic hall church with a height of 81.5 m (267 ft) and has existed in its current form since 1340. It was founded in 1236 by the Bishop of Paderborn, and enlarged at the beginning of the 14th century. Three times a day, a carillon can be heard. The most valuable treasure of this church is a carved altar from Antwerp, decorated with 250 figures. A small museum housed within illustrates the history of the church up to World War II.
The second-largest church is the Neustädter Marienkirche, an early Gothic hall church dating back to 1293. It stands 78 m (256 ft) tall and has a length of 52 m (161 ft). Historically speaking, this building is the most precious. It was the starting point of the Protestant Reformation in Bielefeld in 1553. A valuable wing-altar with 13 pictures, known as the Marienaltar is also kept inside. The original baroque spires were destroyed in World War II, and later replaced by two unusually-shaped Gothic clocktowers.
Bielefeld is also the seat of the two largest Protestant social welfare establishments (Diakonie) in Europe, the von Bodelschwingsche Anstalten Bethel and the Evangelisches Johanneswerk.
Other important cultural sights of the region are the art museum (Kunsthalle) and the Rudolf Oetker concert hall (Rudolf-Oetker-Halle).
On Hünenburg, there is an observation tower.