Linz is the third largest city of Austria and capital of the state of Upper Austria (German: Oberösterreich).

The city was founded by the Romans, who called it "Lentia", but there was already a Celtic settlement called "Lentos", and was first noted in 799 AD. It was a provincial and local government city of the Holy Roman Empire, and an important trading point connecting several routes, on either side of the river Danube from the East to the West and Bohemia and Poland from north to the Balkans and Italy to the south. Being the city where the Habsburg Emperor Friedrich III spent his last years, it was, for a short period of time, the most important city in the empire. It lost its status to Vienna and Prague after the death of the Emperor in 1493.
One important inhabitant of the city was Johannes Kepler, who spent several years of his life in the city studying mathematics. He discovered, on May 15, 1618, the distance-cubed-over-time-squared — or 'third' — law of planetary motion. Kepler is the namesake of the local public university. Another famous citizen was Anton Bruckner, who spent the years between 1855 and 1868 working as a local composer and church organist in the city. The local concert hall "Brucknerhaus" and a local private music and arts university are named after him.
Adolf Hitler was born in the border town of Braunau am Inn but moved to Linz in his childhood, spending most of his youth there. Hitler's parents are buried in the town of Leonding, near Linz. Hitler was enrolled in the Realschule [school], as was the philosopher Ludwig Wittgenstein. Hitler had extensive architectural plans for Linz, and wanted it to be the main cultural centre of the Third Reich. In order to make the city economically vibrant, Hitler initiated a major industrialization of Linz shortly before, and during, World War II. Many factories were dismantled in the newly-acquired Czechoslovakia and then reassembled in Linz, including the Hermann-Göring-Werke (now voestalpine). In addition to an ordnance depot, Linz has a benzol (oil) plant which was bombed during the Oil Campaign on October 16, 1944.
The Mauthausen-Gusen, located near Linz, were the last Nazi concentration camps to be liberated by the Allies. While in operation, they were the source of quarrying for stone for Hitler's prestige projects across the Reich. The main camp in Mauthausen is just 15.6 miles (25km) away from Linz.
After the war, the river Danube that runs through Linz — from the western side to the south-eastern side — which separates the Urfahr district in the north from the rest of Linz — served as the border between the Russian and American occupation troops. The Nibelungen bridge that spans the Danube river from the Hauptplatz (main square) was at that time Linz's version of Checkpoint Charlie. The Nibelungen Brücke with the two bridge head buildings is the only architectural plan Hitler ever carried out in Linz.

The main street "Landstraße" leads from the "Blumauerplatz" to the main square. In the middle of this square the high "Pestsäule" ("plague column", also known as "Dreifaltigkeitssäule" (Dreifaltigkeit means Holy Trinity)) was built to remember the people who died in the plague epidemics.
Near the castle, which is located on the same site as the old Roman fortress Lentia was once built — and also being the former seat of Friedrich the III — the oldest Austrian church is located: Sankt/Saint Martins church. It was built during early medieval Carolingian times.

Other sights include:

• St. Mary's Cathedral (Mariendom), Roman Catholic, in Gothic-Revival style
• Pöstlingberg-Kirche: is situated at the hill Pöstlingberg
• Brucknerhaus — the concert hall named after the composer Anton Bruckner, who was born in Ansfelden, a small town next to Linz.Gugl Stadium, is home to the LASK (Linzer Athletik Sport Klub), which is claimed to be the third oldest soccer club in Austria.
• The Linzer Landestheater is the theater Adolf Hitler and his friend August Kubizek always went to, to hear Wagner.