Drive slowly along the upper reaches of Ponus Ridge and you can glimpse the last vestiges of a once-thriving New Canaan community, most of which now exists deep beneath the Laurel Reservoir. Beyond the chain link fence surrounding the lake, myriad stone walls crisscross through the trees, some of which suddenly disappear into the water. This is all that remains of Dantown. For Bob Tilden of Montour Falls, N.Y., the search for Dantown began as a search for his ancestors. One of these ancestors, Francis Dan, arrived in what was then Stamford in the late 17th Century, eventually settling a community by the Rippowam River near the New York state border.