>>2807140
Buenos Aires fits your requirements anon.

>moderate price
>not hot (unless you visit in Summer)
>interesting architecture
>good nightlife
>you can discover a new continent

https://www.youtube.com/watch?v=LwNOdtYP0Aw
https://www.youtube.com/watch?v=BgFdRw3ul44

Beginner-difficulty South America (you can even drink the tap water)