Congress Avenue Bridge Bats
In summer, Austin's Congress Avenue Bridge is home to 1.5 million Mexican free-tailed bats—the largest urban colony in the world. At sunset they take flight in search of a bite to eat, and the spectacle blackens the Texas sky. The Austin American-Statesman maintains a free viewing area next to the bridge, as well as a bat hotline with the latest flight times.
Tampa Electric Manatee Viewing Center
Apollo Beach, Florida
Hundreds of manatees can be seen from viewing platforms during peak periods (November-April) at this Apollo Beach sanctuary and viewing center presented by Tampa Electric. When Tampa Bay's waters reach 68 degrees or cooler, the warm-blooded mammals bask in the Big Bend Power Station's discharge canal, where clean, salty bay water previously used to cool unit 43 flows back into the bay.
Lincoln Park Zoo
Visit a savannah backed by the Chicago skyline or delve into a tropical rain forest just minutes from Wrigley Field. The animals at Lincoln Park Zoo live in a natural urban oasis—and you can visit every day for free.
The National Zoo
The National Zoo, like most of the Smithsonian Institution's museums and galleries, is free for all. This wild world on Washington, D.C.'s Rock Creek Park is home to some 400 species (a quarter of them endangered), including fan favorites like giant pandas, elephants, gorillas, and tigers.
Lake Washington Ship Canal Locks
This U.S. Army Corps of Engineers site specializes in moving boats back and forth from freshwater lakes to Puget Sound—but its fish ladders help salmon make the same journey. Viewing windows reveal running adult salmon from June to November, ocean-bound salmon smolts in May and June, and the occasional steelhead between January and April.
The Houston Zoo offers free admission on the first Tuesday of every month, from 2 p.m. to closing. A range of attractions includes the zoo’s African Forest and Kipp Aquarium. Interactive Natural Encounters Exhibits get visitors nose-to-nose (through glass of course) with piranha, bats, meerkats, and other exotic animals.
San Francisco Zoo
San Francisco, California
San Francisco residents can visit their hometown zoo free on the first Wednesday of every month and see the penguins, primates, koalas, and other species that share their City by the Bay. The zoo boasts an important botanical collection as well. Proof of residency is required.
Wetlands & Wildlife National Scenic Byway
This byway connects two oases in the Great Plains wetlands. Each spring Cheyenne Bottoms State Wildlife Area and Quivira National Wildlife refuge host many of the shorebirds migrating east of the Rocky Mountains. During this season, the sites teem with 330 species, including pelicans, gulls, herons, ducks, egrets, and even the elusive whooping crane.
Cleveland Metroparks Zoo
Locals rule at the Cleveland Metroparks Zoo, at least on Mondays, when residents of Cuyahoga County and Hinckley Township get free admission. (The RainForest exhibit costs a few dollars more). Monday holidays sometimes bump free admission to the following Tuesday, so be sure to check the calendar on the zoo website.
Are you a Tennessee resident? Then why not spend Tuesday afternoon with some of your furry and feathered friends at the Memphis Zoo? The zoo offers free admission to Tennesseans (with proof of residency) every Tuesday from 2 p.m. to close.
The Shedd Aquarium
This standout aquarium has 52 Community Discount Days per year—and on those days, “discount” means free admission to the facility's original galleries, including Waters of the World, Amazon Rising, and the Caribbean Reef.
Point Reyes National Seashore
The rocky headlands and beaches of Point Reyes are a popular spot for elephant seals, and a growing population of some 1,500 to 2,000 of the enormous animals can be seen here during breeding season from December through March. Be sure to gaze out to sea as well—migrating gray whales can often be seen between January and May.
Saint Louis Zoo
Saint Louis, Missouri
Admission to the zoo is free and offers access to a veritable Noah's Ark of animals, from fierce lions and tigers to petting-friendly bunnies and goats. Fees do apply for some popular attractions, including seasonal sea lion and stingray shows, 3-D movies, and the Zooline Railroad.
The world's largest aquarium wants to help you celebrate your birthday—and their gift is free admission for all Georgia residents on their special day. Naturally, a valid ID or birth certificate is required to take advantage of the deal.
The World Bird Sanctuary
Valley Park, Missouri
See bald eagles, owls, falcons, parrots, and other birds at this sanctuary dedicated to securing the future of threatened species. Free shows and educational programs are also on offer at the facility, which runs a successful captive breeding program, as well as a wildlife hospital that rehabilitates hundreds of birds a year for release into the wild.
Monterey Bay Aquarium
Each December Monterey Bay Aquarium celebrates the holidays with the gift of free admission for Monterey County residents during Community Open House. Valid ID and proof of residence is required for this free look at one of the nation's top aquariums.
National Elk Refuge
See elk grazing in open fields—as they did before European settlers drove them to the Western mountains—in this winter refuge ground near Grand Teton National Park. Between November and April, there are several options for viewing the elk: walking or driving Refuge Road, stopping at paved auto pullouts along Highway 26, or getting up close and personal on a horse-drawn sleigh ride (fee applies).
Suncoast Seabird Sanctuary
This sanctuary on Florida's Gulf Coast bills itself as the largest wild bird hospital and sanctuary in the United States. It brings in some 10,000 wild birds a year to be nursed back to health for re-release into nature. Hundreds of birds are on view here at any given time, from pelicans to birds of prey.
Long Lake National Wildlife Refuge
A massive alkaline lake in North Dakota, surrounded by wetlands and mixed-grass prairie, is a critical migration stop for more than 20,000 gulls, cranes, ducks, geese, and other shorebirds. Some species also breed at the site, which WildBird magazine named a top ten birding locale.
New England Aquarium Lecture Series
The aquarium is more than a fun place to see strange sea creatures—it's also a leader in aquatic conservation and research. Its lecture series includes fascinating free talks by scientists, wildlife photographers, environmental writers, and other experts, followed by a reception. The events are free but reservations are required—get the details online.