The Hudson Valley, Downtown: A New BPC Oasis Is Coming   Ground was broken last month for the newest addition to Battery Park City’s network of parks, a space that Battery Park City Authority President Tim Carey says he envisions "as a glen in the middle of the hills in the Catskills." Teardrop Park, named for the shape of its previous design, is being built on the lot bounded by Murray Street, North End Avenue, Warren Street and River Terrace. Its design, featuring meandering pathways, small waterfalls, and stone outcroppings that can be climbed, is meant to evoke the landscape of the Hudson River Valley. In fact, the park, designed by Michael Van Valkenburgh Associates and artist Ann Hamilton, is being constructed with more than 2,700 tons of stone from Hudson Valley farms and quarries and will feature plants that grow in the valley. When completed, in spring 2004, the park will be surrounded by four residential buildings and will include benches, lawns and play spaces. The waterfall will freeze in the winter, creating a wall of ice.