After trudging up a steep slope the other day, we hikers paused to view acorns that were scattered amid hardened mud alongside an icy trail.

“Look how many there are!” Maggie Jones exclaimed. Stooping for a closer examination, she noticed that several brown nuts, which had fallen from overhanging branches of chestnut oaks, penetrated near-frozen soil.

Nature’s indomitable force was at work: Even in seemingly barren mid-winter, life persevered at Old Lyme’s glorious Upper Three Mile River Preserve.

Maggie, Phil Plouffe and I tramped about three miles earlier this week at the 157-acre preserve, following well-marked, thoughtfully laid-out footpaths that rose and fell more than 600 feet over a relatively short distance.

Mindful of slippery conditions, Maggie and I attached traction spikes to our hiking boots before setting out, but Phil wore only rubber-soled footwear and managed to scramble up and down hillsides that were coated with packed snow and ice, as nimble as a gecko.

Some doubters may have questioned the Old Lyme Land Trust’s 2004 decision to establish this preserve by purchasing a single, land-locked parcel off Four Mile River Road, but over the next 15 years, the nonprofit conservation organization acquired additional abutting parcels, as well as a walking easement across private land, to provide public access.

Today, the preserve is the land trust’s second largest property; the group hopes future expansion will connect it with other tracts to the west, eventually forming a cross-town walking trail.

We began hiking on a white-blazed path at the preserve entrance on the west side of Four Mile River Road, just a few hundred yards north of Exit 71 on Interstate 95. The sound of highway traffic gradually faded as we worked our way north, crossed a pair of shallow streams, and clambered up a lofty ridge.

We watched a pair of ravens wing through a hardwood forest dominated by oaks and birches. Usually, these jet-black birds announce their presence with guttural squawks, but on this day, they remained silent.

With no wind, tree limbs didn’t creak, laurel leaves didn’t rustle. The only sound: crunching boots. We might as well have been hiking in remote Labrador, rather than near a busy highway.

Not one cloud in sight – “a bluebird sky,” Maggie pronounced.

“Perfect day for a hike,” I agreed.

We followed white blazes on a clockwise route, eventually crossing an ice-coated, wooden bridge over a stream at the property’s western boundary. A map refers to this waterway as Threemile River; yet the preserve is called Upper Three Mile River.

Likewise, maps identify a waterway on the east side of Four Mile River Road as Fourmile River. Meanwhile, Eightmile River, which flows northwest of Fourmile River, sometimes is spelled Eight Mile River. Go figure.

After bending north, the white-blazed trail passed through former farmland that was crisscrossed by stone walls and littered with boulders. It’s hard to imagine anyone trying to grow crops on such unforgiving land – no wonder it was abandoned.

Red trail markers overlay white blazes where the preserve passes through private property; hikers are urged to stay on the footpath. The north edge of this property forms a boundary with open space owned by the town of Old Lyme. Eventually, trails may extend into this tract.

For now, though, hikers must head back south on the red-blazed trail and eventually reconnect to the white-blazed trail leading back to the preserve entrance.

The land trust’s website recommends that only experienced hikers traverse the preserve’s rugged trails, but an optional green-trail detour eliminates some of the challenging stretches.

This shortcut, though, bypasses some dramatic scenery. Either way, the Upper Three Mile Preserve is a wonderful sanctuary – “a hidden gem,” Phil said.

A small, unpaved parking area at 106 Four Mile River Load abuts the preserve entrance. Hikers also may park in a commuter lot across the street, near the town’s transfer station.

More information about the preserve, which is open daily from dawn to dusk, as well as the land trust’s other properties, is available at oldlymelandtrust.org.

Incorporated in 1966 as the Old Lyme Conservation Trust, the group’s name was changed to Old Lyme Land Trust in 2010 to emphasize its primary mission – the protection of land.

The trust now owns more than 100 properties covering some 1,100 acres.