Walden Pond

Walden Pond in Concord, MA (42.441212, -71.334528) has one main trail -- a 1.7 mile walking loop that borders the pond. Along the walk, you can enjoy overlooks of the water. Additionally, you can take a side trail and visit the location of Henry David Thoreau's cabin where he lived for two years, two months, and two days. Thoreau later wrote the world-famous book Walden about his experience living in nature. See map, from All Trails, below:

Walden Pond is what is known as a 'kettle pond.' This means that, 15,000 years ago -- during the Wisconsonian stage of glaciation -- a large chunk of ice broke off from the rest of the glacier. The immense weight of that ice, and its eventual melting, formed what we know as Walden Pond today. Walden Pond's shape, as well as its under-water topography, reflects the shape of the original ice block that formed it (1). The following diagram, from the University of Waterloo, provides a simple yet intuitive diagram that illustrates this process:

As you can see from these images, Walden Pond changes in depth quickly. Kettle lakes, because they were formed by glacial fragments, can sometimes be very deep for their size. Walden reaches about 102 to 108 feet at its deepest point (it's the deepest body of water in Massachusetts! (1)). For reference, you can go about 10 miles into the Cape Cod Bay before reaching that depth, while it would take you less than 0.25 miles to reach that depth in Walden Pond.

Above: Geologist and Wildlife Specialist analyzing Walden Pond.

References:

(1) Colman, J. & Friesz, P. (2001). Geohydrology and Limnology of Walden Pond, Concord, Massachusetts. U.S. Geological Survey. https://pubs.usgs.gov/wri/wri014137/pdf/report.pdf.