This morning, crews began stripping away a surface parking lot in Downtown Los Angeles, signaling the start of construction for the second phase of a $750-million mixed-use development. Mack Urban, a Los Angeles-based real estate firm, has teamed with the engineering and construction giant AECOM to develop a series of high-rise buildings on underutilized properties in the South Park neighborhood. At 12th Street and Grand Avenue, plans call for a 37-story structure containing 512 residential units, 10,000 square feet of ground-floor commercial space and a parking garage for 752 vehicles. The building would include a mixture of studio, one-, two- and three-bedroom units, as well as six townhomes along an alley on the east side of the property. The development would also offer residential amenities such as a swimming pool, a fitness center and a nearly half-acre public park to the north of the tower. Elevation plans from architecture firms A.C. Martin and Togawa Smith Martin portray a contemporary glass and steel tower standing approximately 400 feet tall. Previous reports have indicated that 100-foot architectural spire would sit atop the building’s roof. The tower at 1120 S. Grand Avenue is the second component of the Mack Urban-AECOM joint venture to begin construction, following a pair of seven-story buildings on Pico Boulevard. Later phases include a proposed mid-rise structure at 12th and Olive Streets, and two development sites on 11th Street.