Twenty million years ago, nature gave Calvert County a precious gift.

At that time — as continents collided and shorelines began to define themselves — the warm and shallow sea that covered Southern Maryland receded. The cliffs of Calvert County began to erode, with the constant wave and tide action exposing all of the prehistoric species that once dwelled in this place.

And there they remain, these souvenirs of another era — partial shells with the imprints of animals long gone from the Earth. And when a visitor finds such a fossil, be it a shark’s tooth, a part of a whale skeleton or an oyster shell older than time, they delight in holding a piece of the past.

Tourists come to Calvert Cliffs State Park, a secluded beach 4 miles north of Solomons Island, to sift through sand and hoping to find the tooth of a megalodon shark. Some, like 9-year-old Molly Sampson, make headlines for finding something large and special, a megalodon tooth larger than her hand. But most are content to take the nearly 2-mile walk back to their cars with a jar of shells, a few shark teeth and great memories.

“This whole bottle is full of sharks’ teeth,” said Adrian Bernuy, 10, of Germantown, as he showed off what he said was a tooth. (It wasn’t, a common mistake because many of the tiny rocks and fossils can be indistinguishable to the untrained eye.)

Adrian’s mother, Svetlana Trofimenko, took time off from her U.S. Postal Service job to take her son to the beach.

The walk to the small, cliffside beach overlooking a liquid natural gas shipping terminal nearby is almost as exciting for young visitors like Adrian as the beach itself. Along the way, he reported seeing dragonflies, snakes and lizards — iridescent skinks that climb along the wooded walkways over lush wetlands. We also spotted tiger swallowtail butterflies, rare mushrooms and a tropical-looking plant called arrow arum with roots that bent like thick extension cords.

Considering how special the place is, I find it perplexing how easy it is to reach.

Calvert Cliffs State Park is just off Routes 2/4, less than an hour south of Annapolis. You can make a fun full day of a trip there with a morning at the beach and an afternoon at the Calvert Marine Museum in Solomons, with a stop for a seafood lunch. Even on a scorching or humid day, the nearly 2-mile walk to the beach is shaded, pleasant and rarely crowded. It gives you time to notice the nature all around.

“We just wanted to go somewhere different,” said Karen Adams, who was walking near the cliffs with her grandson, Hayden.

The family had come to Maryland from their home in suburban Cincinnati. As far as something different, the mission was accomplished. Hayden enjoyed all the shells, oyster drills and fossils he saw on the beach. Most of their extended family stayed back to fish; he couldn’t wait to tell them what they missed.

Conor and Emma Bridge passed the time on the hike to the beach singing songs — “Hi, I’m Bob, your very best friend. If you don’t give me money, this song will never end” — and enjoying the frogs, birds and buzzing flies they could hear as they neared the Chesapeake Bay.

The siblings came from College Station, Texas, to visit their grandparents.

“You need to get a net,” Emma, 10, told me when she saw that all I had was a notebook, a pen and a bottle of water. “How are you going to get any like that?”

Emma’s own sifting net was filled with sand, pebbles and a few keeper pieces. Her grandparents’ two dogs, Snickers and Oprah, chilled on the beach until they saw another dog, which prompted a bark-off that interrupted the quiet for a few minutes.

Ivy Woodford, 11, probably found the day’s biggest treasure during our visit — a rock the size of an iPad, with imprints from fossilized shells. Her plan was to take it home to Mount Airy and put it in her garden. But not before, she said, she showed it to some people.

Her mother, Kate Woodford, an ER nurse, said she was glad to get out for the day, get away from screens and air conditioning, and enjoy an educational day at the beach.

“It’s a nice place to unplug, a nice hike and nice to do something different,” she said.