Hola Shirley, There are one or two lessons in Kwiziq on the topic of what I call “unexpected” definite articles [for English speakers anyway], but many outstanding queries remain. I recall Inma or another of the teachers saying that it is a very complex subject, that within the format used by Kwiziq it would be difficult to do a comprehensive overview. 

I have a textbook “A New Reference Grammar of Modern Spanish” by John Butt and Carmen Benjamin. It is still in print. In the 3rd edition, Chapter 3 “Articles,” on pages 31 to 42 inclusive, there is a superb explanation of this topic. It covers 12 pages so you can see what the teachers mean by complex. Nonetheless it is “gold dust” and makes very good reading.

I’m not qualified to say for sure, Inma can clarify, but I think the explanation for “La Universidad” falls under the heading 3.2.27 of the book above that ”Phrases denoting Place” require the definite article in Spanish. They quote examples like “en el escenario [on stage], “en el espacio” [in space], “debajo de la tierra” [underground], “al/en el/del hospital” [to/in/from hospital], “en el colegio / la iglesia” [in school, church]. 

I hope that helps - good reading if you can get the book. The older editions are much cheaper than the newer ones; only a few £’s or €’s.

Saludos. John