This building used to house both elephants and hippos, but the elephants moved out some years ago, and their part of the building - as seen on this building - has now been converted into a small museum for osteozoology. There's also a small exhibition on the history of the elephants in Riga.
There is an extensive, 6-page review of Riga Zoo in the latest issue of Zoo Grapevine & International Zoo News, and there is mention that the Elephant House contains only two elderly female common hippos, as well as some ponies in the outdoor enclosure, but no other animals. It will be interesting to see what the zoo does with this building once the hippos are deceased.
As mentioned, it's a museum of osteozoology so I guess they could easily keep it like that.
What did the Grapevine reviewer think of the zoo? I thought it was surprisingly extensive for a zoo that's hardly ever mentioned here on Zoochat, and while the place does bear the mark of being a former Soviet zoo in a (by European standards) relatively poor country, most of the exhibits were passable, a few even pretty good (for example the new tiger exhibit and the reptile exhibits). I was especially impressed by the huge amphibian collection.
@Hvedekorn The Grapevine reviewer (Tomasz Doron) spent two days at Riga Zoo in January 2020 and his 6-page article contains 13 photos of varying sizes as well as the text. There is a great section on the zoo's history, as well as a comprehensive tour of the facility. It appears that there really aren't a lot of big-name mammals, but instead Riga Zoo is famous for smaller creatures. There is mention of 69 invertebrate species, 70 fish species, as well as 46 amphibian species, with all those numbers being really impressive. The Tropical House holds a nice collection, including a nocturnal hall with the likes of Ground Cuscus, Brush-tailed Bettong, Malagasy Giant Jumping Rat, Northern Luzon Cloud Rat and Rock Cavy. Elsewhere, Chinese Dholes and European Golden Jackals would be great to see.