After three of us scrambled this week up a series of rocky ridges leading to a modest summit generously called Popp Mountain, we caught a distant glimpse of a glittering body of water.

This was the Saugatuck Reservoir, which spreads out over 880 heavily forested acres straddling the Fairfield County towns of Redding, Weston and Easton.

Had Phil Plouffe, Andy Lynn and I climbed this hill a century ago, we would have gazed at Valley Forge, a village where the nation’s first iron plows once were manufactured. This tiny hamlet (not to be confused with the Revolutionary War encampment in Pennsylvania) had been settled by Welsh immigrants in 1760. Connecticut’s Valley Forge now lies some 100 feet underwater.

Construction of a dam on the Saugatuck River in 1945 to create the reservoir followed a long, bitter and ultimately futile fight by displaced residents.

Another legal battle had a different outcome in 1999, when a coalition of environmental groups blocked the water company from selling 730 acres to a developer who planned to build a gated community with 103 luxury homes and golf course. Supported by actor Paul Newman, who lived in nearby Westport, they raised $5.3 million to buy the property; the state kicked in the remaining $6 million.

Today, the Trout Brook Valley preserve, owned and managed by the Aspetuck Land Trust, is a pristine swath of open space that features 13 miles of hiking trails. It also abuts the 162-acre Crow Hill and 117-acre Jump Hill preserves, crisscrossed by an additional 6.4 miles of footpaths.

The three parcels form the core of a 6,400-acre expanse that “serves as the green heart of Fairfield County,” the land trust notes.

Phil, Andy and I wound up hiking a six-mile loop in the Trout Valley section, starting and ending at the southwest corner, not far from Valley Forge Road.

“These are some of the best-marked trails I’ve ever seen. Even WE can’t get lost,” I said. Our hiking group has been known to take a wrong turn or two. Just to be safe, though, Andy took a photo of the trail map, while Phil grabbed a paper copy.

We started out on the Green Trail, designated as “easy,” and almost immediately veered off onto the Red Trail, rated “difficult.”

“Shouldn’t be too hard for you guys,” I said. Andy returned last week from a 17-day trek in Nepal’s Himalayas, reaching an elevation of 17,400 feet, at the same time Phil was climbing 14,000-foot, snow-covered peaks in Colorado’s Rockies. Those excursions, though demanding, did not require technical gear.

Ironically, we did use a rope while scaling a short but steep stretch on 351-foot Popp Mountain. Land trust volunteers had installed the line to help hikers make the climb.

The trail eventually smoothed out and we followed a ridge line, surrounded by bare oaks, beech and birches, with swatches of green pines and mountain laurel. The forest in late autumn and winter, after leaves have fallen, rewards hikers with expansive views of undulating terrain.

In about three miles, we reached the end of the Red Trail, at the intersection of the White Trail. Had we continued north, we could have entered the Jump Hill preserve, but decided to stick with Trout Valley and return south.

A few hundred yards later, the Yellow Trail beckoned. Using the trail map, I saw that Yellow was rated “difficult.” The White Trail we were hiking on was “easy.”

“We’ve already done three miles of ‘difficult,’” I said, “I think we should reward ourselves with an easy trail.”

Phil and Andy agreed.

The last three miles indeed were effortless. The trail eventually opened up to a wide, smooth, packed-gravel road – no tripping over tree roots, slipping on moss-covered rocks or using a fixed rope to ascend a jumbled ridge.

Had we explored the rest of the preserve, we could have rambled over a wide assortment of other color-coded trails – green, orange, blue and pink, marking not just degrees of difficulty but also sections open to dogs and horses.

We also could have downloaded a Trout Brook Valley GPS trail map on our smartphones, using the Avenza Maps app, but that would have been overkill. In addition to colors and signs, the trail is marked by numbers to keep wayward hikers on track.

We hikers are forever indebted to those who donated time and money to keep this resplendent parcel unspoiled and open to the public, rather than a sealed-off enclave for Fairfield County’s privileged.

The county in the state’s southwest corner already has plenty of upscale communities in Greenwich, Darien and New Canaan, but also has some of the state’s poorest neighborhoods in Bridgeport.

Nature preserves are open to all.

We accessed a trailhead on Bradley Road, just off Valley Forge Road.

There are other parking options at Black Rock, Freeborn Road, Wells, Wyldewood and Woodland Road roads. More information: aspetucklandtrust.org/trout-brook-valley-preserve.