In 50 years, urban sprawl has turned the 40-acre Hidden Valley Camp into a wilderness area inside the city.

“I think it just adds to your appreciation of Lawrence that we have something here that is very unique,” said Karen Warner, chairwoman of the Friends of Hidden Valley. “You can’t find camps around. It’s kind of like Central Park in New York. It’s just a wonderful thing, and we want it to be available for our children and our grandchildren.”

But many Lawrence residents other than Girl Scouts have never seen the inside of the private site near Kasold Drive and Bob Billings Parkway.

As part of Hidden Valley’s 50th birthday, the public can catch a glimpse Saturday afternoon of the urban campground.

Girl Scout troops have camped at Hidden Valley for a half-century after organizing founders purchased the land. From 2 p.m. to 5 p.m. Saturday, anyone can stop by and explore the grounds and its trails.

“For people who have never seen it, this is their chance to see what the camp looks like,” Warner said.

The event will include games, prizes and birthday cake and ice cream. It is the fourth and final celebration this year in honor of the campground and its founders.

The Friends of Hidden Valley oversee the campsite, which has a manager, Durand Reiber. Other than funding from the Bromelsick Trust, the organization relies on donations from members to pay maintenance costs.

Hidden Valley now features a pond and other hiking trails in addition to the campsite.

“We want the whole town to see what Hidden Valley is like and to understand what a great facility it is for Lawrence,” Warner said.

Many Girl Scouts and Friends of Hidden Valley have used the urban wilderness for camping and other outings during the last 50 years.

“It’s unlike anything else that the girls could experience because it is just nature. It’s primitive out there,” Warner said.