I have been wondering for a long time who paid for the construction of the city wall of Krems in Lower Austria. I recently found a news report from 2002 that discusses the planned renovation of the old city wall and gives the context of original construction as the the reign of Emperor Friedrich III, specifically 1477 to 1480.
Now that the funding situation is clarified, the context needs to be taken into consideration. A look at the chronicle of the museum of Lower Austria shows that, while Friedrich's control of Lower Austria was continuously contested during his reign, partially by his younger brother Albrecht VI, partially by his neighbor Matthias Corvinus, Friedrich III persistently invested into the economic improvements of Lower Austria. He gave salt trading rights to Retz (1458) and made Weißenkirchen into a market (1459) for the Wachau. Despite his brother Abrecht VI having nominal control over Lower Austria since December of 1462, Friedrich gave the right to deposit goods (Niederlagsrecht) to Stein and Krems and to trade Venitian goods via Mariazell. He also granted improvements to the coat of arms for Stein and Krems in 1463, as well as the right to construct a bridge between Krems and Mautern on the southern bank of the Danube (which got its coat of arms from Friedrich in 1467).
By December of 1463, Albrecht VI had died and the estates recognized Friedrich III as the ruler of Lower Austria. However, 1476 Matthias Corvinus captured the eastern part of Lower Austria, and only the Peace of Korneuburg and Gmunden of 1477 quelled the competition, until the war broke out again in 1482. So the fortification of Krems belongs into two contexts, the preparations of Friedrich III for more hostility with respect to Lower Austria, and the general development of the geographic base of the Hapsburg empire.