Lehen is a district in the northern parts of Salzburg, on the left side of the River Salzach. In terms of population, Lehen′s 15,000 residents make it the biggest of Salzburg′s districts. In fact, this is largely due to the high population density. Lehen has a reputation for being a shit area, with loads of immigrants and a low standard of living. However, this applies only to some sections of the area, mainly in the south and along the two major roads of the Ignaz-Harrer-Straße ("Kebab Mile") and the Rudolf-Biebel-Straße. These two streets are famously crowded with frequent congestions.
For centuries, Lehen was an agricultural village. Several large farms are still preserved, even though they might have undergone strong alterations. Note the Rauchmühle, the Annahof or Lürzerhof (the latter was developed into a small castle). There was an army base in Lehen until 1900, which prevented the area from being used up for other buildings. Only after WWI, Lehen really took off, at an accelerated pace after WWII. Especially since the 1950ies, Lehen is generally associated with lots of foreigners who choose to live here due to the affordable real estate.
Until around 2000, Lehen was also known as the location where the football stadium was to be found. It was later demolished after the opening of the current Salzburg Stadium. Since the 1990ies, the city tries hard to improve the general appearance of Lehen. The city′s central library partly moved into Lehen; the Literaturhaus Salzburg can be found here; and with the development of the local railway network, the district is supposed to get more attractive in general.
In terms of sightseeing attractions, there is little to point out. The private medical university Paracelsus has its headquarter here, even though much of the teaching is done on other premises. Note the parish church St. Vinzenz Palotti, which is managed by the monks of the Johannesschlössl on the Mönchsberg. The church is one of many post-WWII churches in Salzburg and was consecrated in 1964.
Lehen on the German Wikipedia
City of Salzburg, Official Website