We went to Riga in October last year, but it was unseasonably warm.
Old city is beautiful, a big mash of higgledy piggeldy medieval streets, some great old buildings, lots of cool bars and restaurants. This place by the old city walls was brilliant, really traditional food by the old city walls:
http://www.latvianfood.lv/
Next to the old city is a big beautiful park with the river running through it and in the newer part of the city there are some amazing Art Deco buildings, huge market built in old Zeppelin hangars and, again, some great bars and restaurants. Loads to see and do just wandering around.
We went for MrsIHN’s 40th and got a ridiculous deal here:
https://grandpoet.semarahhotels.com/lv
It were right swanky, champagne for breakfast and everything 🙂 5/10 minute walk through the park to the old city too, great location.