In the latest sign of investment for downtown Sunnyvale’s central core, developers have broken ground on three towers that will add 590K SF of office space and 479 apartments to the area.

The new components are part of Cityline Sunnyvale, a mixed-use project led by STC Venture, a joint venture between Cupertino-based Hunter Storm and Sares Regis Group of Northern California. The venture was formed in 2016, and about three years later, the city approved its plan for 817 residences, 709K SF of office and 642K SF of ground-level retail.

STC has since delivered 273 apartments and hundreds of thousands of square feet of retail space, which is walking distance to Caltrain and is leased up, the company said in a statement.

As part of the second phase, the company broke ground this week on two seven-story office towers that will include rentable office, retail, flex and outdoor terrace space; a 12-story apartment building dubbed The Martin that will include 53 affordable units, ground-floor retail and restaurant spaces and “hospitality-level” amenities; and a public park to function as a town square.

Cityline Sunnyvale is anchored by the 52K SF AMC Dine-In Sunnyvale 12 and a 52K SF Whole Foods Market, both of which opened last year in the heart of the project. The first phase also included a 198-unit rental project called The Flats, which has about 100K SF of ground-floor retail as well as a Target.

“Looking back at our progress over the last five years, we are grateful for the opportunity to transform this community in such a profound way,” Drew Hudacek, chief investment officer of SRGNC, said in a statement.

The pandemic has delayed the project’s construction timeline; the second phase was slated to kick off groundwork last spring. The three buildings are now scheduled to deliver in late 2024.

Architecture and design firm Heller Manus has been tapped for the residential tower, while Gensler will design the two offices. Devcon Construction is the contractor for the office project and Build Group is the contractor for the residential portion.

“These 590,000 square feet of new office and retail space will bring more jobs to the central core of Sunnyvale and boost business for all of the community’s business owners,” Hunter Properties President Deke Hunter said in the statement. “With Caltrain just blocks away, we are solidifying downtown Sunnyvale as a transit-oriented community that can attract visitors from throughout the region to work and shop here.”