Oregon Zoo, Portland (must see)

The state's most popular tourist attraction, this zoo, opened in 1888, is foremost known for its elephants – the most successful breeding herd in captivity. Africa-themed exhibits feature some of the best habitats with a man-made (yet very lifelike) rainforest and a savanna populated by rhinos, zebras, giraffes, and hippos. Among other highlights are the two otter tanks – one in Steller Cove with sea otters, the other in the Cascade Stream exhibit with river otters frolicking alongside beavers, ringtails and many birds. In the summer, they have an exceptional outdoor concert series with lawn sitting, "rain or shine". There are also places to grab drinks, and a much-loved miniature train pulled by a real steam engine puffs around the zoo and on a four-mile loop to the International Rose Test Garden and Portland Japanese Garden. Kids will love it!

Why You Should Visit:
Most exhibits feature multiple viewing locations so it feels like there is room for everyone to get a good look.
Also, most viewing areas are under cover and it's not too far a dash from one place to the next in case of rain.
And again, most exhibits allow for the animals to move around more based on their preference.