You've heard of the famous beaches, like Waikiki Beach or Venice Beach, but there are wonderful beaches that are a little more serene and certainly less crowded, making them true best kept travel secrets. Observe a large variety of wildlife at Caladesi Island State Park in Florida, accessible only by private boat or ferry. See purple sand at Pfeiffer Beach in Big Sur, California, caused by manganese garnet particles that wash down the hillside. Walk along the pebbles at Orient Beach in New York and find yourself at the Long Beach Bar Lighthouse. Rugged Ruby Beach in Washington has unusual rock outcroppings that seem somewhat other-worldly.

What's better on a hot summer day than jumping into a cool swimming hole with a big splash? The Blue Hole in Santa Rosa, New Mexico is a crystal clear-blue artesian well that stays a pleasant 64 degrees Fahrenheit year-round. It's a favorite of scuba divers, with visibility up to 80 feet. Another Blue Hole, located in Wimberley, Texas, is part of Blue Hole Regional Park, offering a cool, spring-fed blue pool perfect for swimming or lazing around on an inner tube with its famous rope swings. Peekamoose Blue Hole in New York offers a cold, deep, aqua-colored pool nestled in the Catskills for a legendary summer dip.

Who says you have to go abroad to see castles? Impressive strongholds and architectural marvels are among America’s best kept travel secrets. Bishop Castle in Rye, Colorado features grand Gothic-style architecture built by hand, complete with a fire-breathing dragon spout. Wing’s Castle in New York was the creative brainchild of Peter and Toni Ann Wing, constructed from 80% recycled materials and offering bed-and-breakfast stays. In Salisbury Park in Massachusetts stands Bancroft Tower, a miniature stone castle erected in 1900 that is listed on the National Register of Historic Places. If you enjoy architectural mysteries, you might also like exploring mysterious underground caverns across the country.

Caves and caverns are located all over the United States, and while spots like Carlsbad Caverns and Mammoth Cave get the headlines, lesser-known subterranean wonders make fantastic day trips. The Smallin Civil War Cave in Ozark, Missouri was used for military activities during the Civil War and features guided walking trails past beautiful underground waterfalls. Secret Cavern in Cobleskill, New York offers guided tours past stalactites and stalagmites leading to a 100-foot underground waterfall. At Kartchner Caverns State Park in Arizona, visitors can view glittery quartz formations alongside an 80,000-year-old Shasta ground sloth fossil.

Everyone’s heard of Yosemite or Yellowstone National Parks, but lesser-known state parks deserve just as much attention. Fall Creek Falls State Park in Tennessee boasts a magnificent network of hiking trails surrounding the stunning 256-foot Fall Creek Falls. John Pennekamp Coral Reef State Park in Key Largo, Florida offers glass-bottom boat tours for close-up views of colorful marine life. Custer State Park in South Dakota’s Black Hills allows visitors to experience wild bison roaming freely across sprawling sanctuary lands. These quiet parks offer a fantastic alternative to unspoiled secret beaches for nature lovers.

Captivating art installations can be found where you least expect them. Visit the Heidelberg Project in Detroit, Michigan, an outdoor community art environment created by Tyree Guyton using polka dots and salvaged objects. In Wilson, North Carolina, marvel at Vollis Simpson’s Whirligigs, an extraordinary park filled with giant kinetic wind sculptures. In Kansas, stop by the unique Dinosaur Not So National Park created at the Dorris place, featuring over 20 large welded dinosaur skeleton replicas.

Forget overcrowding at the Smithsonian or the Metropolitan Museum of Art when discovering secrets of America's favorite places. Head off to The Museum of Wonder in Seale, Alabama, where a dirt road and the #41 on a mailbox mark a drive-thru cabin filled with over 10,000 oddities and curiosities. In the Pacific Northwest, make sure to visit the Rice Northwest Museum of Rocks and Minerals in Hillsboro, Oregon. Listed on the National Register of Historic Places, the museum houses the world's largest opal-filled thunderegg and an extensive collection of rare meteorites.

The secrets are out! I’m now wondering how many of America’s best kept travel secrets are, in fact, secrets! Do you have a secret destination or hidden attraction to pass on? (Go on – this is one time when spilling the beans is a good thing!)