The Latvian National Theatre at Kronvalda 2. While I was in Riga they were preparing for a production of Cyrano de Bergerac in Latvian. Much as I'd have loved to see it, I couldn't hang around till the opening. I did however get to see Handel's Alcina at the Opera House and can strongly recommend going to see anything there. Gorgeous little venue and the terrace of the first floor bar is a great place to view the city from.