What is "heerlen"

Heerlen (; ) is a city and a municipality in the southeast of the Netherlands. It is the fourth largest municipality in the province of Limburg.

Heerlen forms part of Parkstad Limburg, formerly known as Oostelijke Mijnstreek (Eastern Coal Mining District), an agglomeration with about 220,000 inhabitants.

After its early Roman beginnings and a modest medieval period, Heerlen became a centre for the coal mining industry in the Netherlands in the late 19th century. In the 20th century, architect Frits Peutz played a major role in shaping the city as we know it today. His most famous design, and a distinctive building in the city centre, is the so-called Glaspaleis (Glass Palace), listed as one of the world's thousand most architecturally important buildings of the 20th century.