The Emerald Necklace at Jamaica Pond in Autumn

Olmsted's Long Green Chain, Link by Shining Link

Jamaica Pond is the largest standing body of fresh water in Boston - sixty-eight acres of glacial kettle pond, spring-fed and clean, surrounded by a 1.5-mile walking path that is part of Frederick Law Olmsted's Emerald Necklace, the chain of parks that links Boston Common to Franklin Park in a continuous ribbon of green. I walked the pond on a morning in late October, when the beeches and red maples along the shore were in full color and the water reflected them so faithfully that it was difficult to tell where the trees ended and the pond began.

The path starts at the boathouse on the north shore - a modest structure that rents rowboats and sailboats from April through October - and circles the pond clockwise. The first stretch runs through a grove of weeping willows that trail their branches in the water, creating a green curtain between the path and the pond. Joggers passed me at intervals. An elderly man walked a dachshund whose legs were so short it appeared to be swimming through the fallen leaves.

Jamaica Pond is deep - fifty-three feet at its center - and the water is remarkably clear for a body of water surrounded by a city of 700,000 people. The springs that feed it rise from the gravel bottom, and on a still morning, you can see fish moving in the shallows - stocked trout, largemouth bass, chain pickerel. Fishing is permitted with a Massachusetts freshwater license, and on weekends the serious anglers claim spots on the western shore at dawn, setting up folding chairs and thermoses with the proprietary calm of people who have done this for decades.

Olmsted designed the landscape around Jamaica Pond in the 1890s, and his touch is visible in the way the path curves to reveal views gradually - the boathouse disappearing behind a grove as you walk south, the Francis Parkman memorial bandstand appearing as you round the western end, the Jamaicaway road hidden behind a planted berm so effectively that you forget it exists. The genius of Olmsted's parks is this editing - not what he added, but what he concealed, shaping the experience by controlling what you see and when you see it.

The southern shore is the quietest section, shaded by tall oaks and beeches, with benches placed at intervals that suggest someone calculated the ideal distance between moments of sitting and moments of walking. I sat on one and watched a great blue heron fish the shallows near the outlet, striking with that sudden, violent thrust that always startles, no matter how many times you see it. The heron came up with a small perch, swallowed it whole, and resumed its stillness.

Jamaica Pond is free, open year-round, and accessible by the Orange Line to Jamaica Plain station. Come in October for the foliage. Come in July for the sailing. Come in any month to walk a path that Olmsted designed with the specific intention of making city dwellers feel, for an hour, that they had left the city. A hundred and thirty years later, the trick still works. The city is right there, beyond the trees, and you cannot see it, and you do not think of it, and that is the design working exactly as intended.