@BlackRhino: there are a number of top quality hippo pools in the U.S., and the best ones invariably have underwater viewing as that can really elevate a good hippo pool and allow it to become a great one. San Diego's is fantastic, but the Toledo Zoo is massive and holds up quite well 20 years after it was built.
I still love Toledo's but I just think San Diego's is the best. It feels more new and I like how the Ituri Forest area is themed. Plus the hippos have plants and logs in their exhibit whether than just on the outside.
Does anyone know for sure what is happening with the proposed construction in the African area of the zoo? It's difficult to believe that the hippo exhibit might be enlarged, as it is already quite impressive in size. That's great news for such massive animals.