Short answers, pulled from the story.
Castra Regina was constructed in the year 90 at the confluence of the Danube, Naab, and Regen rivers. Archaeological evidence places the original camp east of today's Obere Bachgasse and west of Schwanenplatz within the city core.
The Imperial Diet established its headquarters in Regensburg in the year 1663 to create what historians call the Perpetual Diet. This unique configuration lasted until 1806, transforming the city into one of Europe's most significant diplomatic hubs.
Nazi forces destroyed the Regensburg Synagogue and arrested around 220 Jews during Kristallnacht on the 9th of November 1938. Some deportees were sent to Dachau concentration camp while others faced deportation to Piaski in German-occupied Poland or Theresienstadt Ghetto in Czechoslovakia by 1942.
Siemens became the first multinational corporation to establish operations in Regensburg during the early 1960s. BMW opened its automobile production plant in 1986, and high-tech companies including Infineon and OSRAM set up headquarters in the city by the 1990s.
The World Heritage Committee listed Regensburg's Old Town as a UNESCO site in July 2006 due to its well-preserved medieval architecture. Nearly 1,500 buildings remain listed within the historic district, making it the largest intact medieval old town north of the Alps.