My first experience with a known parking lot to park conversion was Halcyon Commons here in Berkeley. The community-initiated park was designed over the course of four years and was led by the Halcyon Neighborhood Association. City funding, sweat equity, and contributions from local businesses transformed the 28-space parking lot into a 0.2-acre municipal park (with stewardship by the neighborhood association) with "a tire swing, a community bulletin board, a community herb and flower garden, a wisteria-covered arbor, a grass field, and many trees and flowering bushes." Check out the the new gate.
Across the country, in Pittsburgh, Pennsylvania, Schenley Plaza was recently restored from a parking lot to its former status as a 5-acre public park. The restoration was spearheaded by the Pittsburgh Park Conservancy, a nonprofit conservancy that manages Pittsburgh's four large parks: Schenley, Frick, Highland, and Riverview. Schenley Plaza follows the design and management precedent set by Bryant Park in New York City: moveable chairs and tables, a generous lawn area (1 acre in the case of Schenley), programmed activities, and a restaurant, among other things.
Other "unpaving the city surface" (Marcus Farr, Cite, Winter 2006) designs include Discovery Green in Houston, Grant and Millennium Parks in Chicago, Boston Common and Post Office Square in Boston. The latter park, according to Farr, was constructed when a five-story garage was undergrounded and created "1.7 acres of accessible and well-used downtown greenspace." Farr observes that the integration of infrastructure (parking) and greenspace can limit heat islands and satisfy "aesthetic needs."
Parking area redesign is not limited to reducing urban heat islands. The use of permeable paving has great watershed benefits: stormwater is intercepted, reducing the volume of runoff into the storm-sewer system as well as filtering pollutants as rainfall percolates through the soil beneath the pavers. Local examples, like the Wellman Courtyard on the UC Berkeley campus, have been documented by Blue-Green Building:
Above, in a courtyard among Beaux Arts buildings, pavers set in a sand base let rain soak in. Some pollutants are filtered out, and some water soaks into the native clay soil beneath. A perforated-pipe underdrain takes heavy flows to the storm drain, preventing floods.