This is one of the best zoos I have ever been to. They make great usage of the land they have and have a good selection of animals to see.
Keep in mind the zoo grounds are hillie and step so walking is tiring at times.

The larger animals were not outside or were sleeping when we were there. We sat and watched the orangutans inside for quite awhile, they always amaze us. However, we didn't see any lions or tigers and the pandas were inside as well. None of the animals were active. We went on a cooler day, maybe low 50's and we went around 2:30.

I try and see the zoo every time I visit D.C. It is well maintained and free! You are allowed to bring in food and drink and I would definitely recommend that, the food there is not great and expensive.

We had a great time with our 9 year old on Spring Break. She loved the Panda Exhibit. The fact there is no charge to enter was great also. If you plan to drive and park be sure to arrive early to make sure all of the parking spots are not full. Also plan to pay $25 for the day to park. Now when you get hungry I suggest to bring snacks and water as outside snacks are allowed but you still have to go through a security check and go through a metal detector. If you eat inside at one of the on-site food places be prepared to pay a lot for not so fast food. Took us over 25 minutes for two slices of pizza and 1 kids chicken strips. The lost track of who had been served and came out asking for customer copies of the receipt so they could fill orders. After 5 people that ordered after me got their food our ticket was finally called. Seating was very limited but me managed to share a table with some nice visitors. Once we finished we continued our tour and came across another food place not far from the one we were at and no lines with places to sit. Just check around before deciding you may find a spot not so crazy and have better service. Exhibits were great and they put Easter eggs out for the Gorillas with treats and that was fun to watch as they found the eggs with treats. Great place especially for free entry.