I had never seen such a large river totally frozen. That's the Daugava in Riga. This is my second time there, and my first during winter time. My advice is that you plan to visit this beautiful city, better do it during summer time. Temperature here has been way below zero for weeks.
I'm here on business, and I may need to stay more than 2 weeks. I'm dreaming of the warmer climes where I used to live.