Starting at the Boston Common, but easily picked up at any point along the way, the Freedom Trail offers historical insight into the city and its surroundings. Easy to "hop on and off", the Freedom Trail weaves throughout the city and highlights some of Boston's most special places, including Park Street Church, the Old State House, Faneuil Hall, Paul Revere House and the USS Constitution.
Photo courtesy of Massachusetts Office of Travel & Tourism

The Bellagio is home to not one but two of the best free attractions in Las Vegas. The intricately designed floral displays at the Bellagio’s Conservatory fill the space all the way to the glass and metal roof, which looks like it belongs someplace with a much longer history than Vegas. It’s surprising to find this small horticultural oasis in a casino, but it’s a good surprise. The Bellagio’s Fountains are one of Las Vegas’ most photogenic attractions, wowing crowds several times a day with a musically synchronized water dance.
Photo courtesy of Bellagio

A veritable living plant museum, the United States Botanic Garden in Washington, DC features colorful flowers and greenery year round, whether within the state-of-the-art Conservatory or in the series of outdoor gardens. Bartholdi Park, located just across the street from the Conservatory, features a lovely fountain by Frédéric Auguste Bartholdi, the same French sculptor who envisioned the Statue of Liberty.
Photo courtesy of U.S. Botanic Garden

With over 85 cultural and recreational facilities, Balboa Park is a must-see in San Diego. The zoo is a big attraction, but there are also 15 museums, cultural centers, lawn bowling, a carousel, a botanical building and a miniature railroad ride. Getting around the massive complex is easy, thanks to the free tram. Entrance to the park is free; attractions within the park are priced individually.
Photo courtesy of Thinkstock

The National Mall and Memorial Parks of Washington, DC pack a big patriotic punch. The park encompasses numerous cultural icons within the same area, including the Lincoln Memorial, Washington Monument, Jefferson Memorial, Vietnam Veterans Memorial and Ford's Theatre National Historic Site, to name just a few.
Photo courtesy of Thinkstock

New York's iconic Central Park burst from the minds of visionaries Frederic Law Olmsted and Calvert Vaux, setting a new standard for urban park design. Joggers, nature lovers, and bikers use the park daily. Kids young and old enjoy skating at Wollman Rink, visiting the Central Park Zoo, and riding the Friedsam Memorial Carousel. The Great Lawn is home to free live performances by the New York Philharmonic, while the Delacorte Theater sets the stage for Shakespeare in the Park and SummerStage takes over Rumsey Playfield during warm months.
Photo courtesy of NYC & Company / Christopher Postlewaite

The Alamo Mission in Texas has a rich history that spans more than 300 years. It is most famous as the site of the historic Battle of the Alamo in 1836, a major event in the Texas Revolution. Today, the Alamo complex is a museum that serves to inspire Texans and visitors alike. See exhibits about the revolution and state history. It is a reminder of the sacrifice many made for liberty, and the San Antonio attraction draws more than 2.5 million visitors every year. “Remember the Alamo!”
Photo courtesy of Visit San Antonio

Parking and admission are both free at the beautiful Birmingham Botanical Gardens in Alabama. The 67.5-acre garden features more than 3,000 taxa of plants spread across 25-plus themed gardens, including a Japanese garden complete with a tea house, a wildflower garden with Alabama native plants and a fern glade with more than 100 types of ferns.
Photo courtesy of Natalie C / Flickr

The stunning red sandstone formations outside of Colorado Springs, appropriately named the Garden of the Gods, are completely free for visitors to enjoy. Paved and unpaved trails wind through the formations, and a free visitors center doubles as an excellent natural history museum for the park. Naturalists lead free guided walks daily.
Photo courtesy of Thinkstock

The 90-acre St. Louis Zoo exhibits 600 species of animals representing every continent and major biome on the planet. It's also one of the nation's few zoos that offers free entry, though some exhibits and shows charge smaller admission fees. The zoo's Penguin & Puffin Coast exhibit is one of the best penguin habitats in the country, with four species of penguins and two species of puffins on display.
Photo courtesy of AP Photo/Jeff Roberson