LAWRENCE — An hour isn’t long enough to explore historic and diverse Den Rock Park.

Located off Route 114 and bordered by Lawrence, North Andover and Andover, the park is made up of just 120 acres of land, but contains a lifetime’s worth of outdoor experiences.

“I’ve been coming here for 25 years, and every time I return, I see something I’ve never seen before,” Tennis Lily, chairman of the Lawrence Conservation Commission, said during a mid-morning walk Wednesday on a short loop of the park’s several miles of winding trails.

“It wasn’t until a year ago that I saw my first deer here,” he said. “I followed a family of them for three hours, taking pictures. This is an incredibly diverse habitat. Right in the middle of an urban setting, you can see deer, coyote, fox, river otter, possum and dozens of different kinds of bird species, along with endangered plants and animals you can’t find outside the park.”

According to a write-up in the Andovers Trail Guide, the land that makes up the park was purchased by the city in 1877 originally for use as a cemetery. It was changed into a city park in 1896, and was improved in the 1930s by the Civilian Conservation Corps and the Works Progress Administration, whose workers built trails, two amphitheaters, and a boardwalk, among other improvements.

Over the years, the park has been used as a source of stone for the construction of nearby Interstate 495, as a dumping area for city composting material, and was even eyed for development as the site of a mall.

It was this last threat that galvanized Lilly to action. He and others in the city fended off the mall developers, protecting the park for future generations