SAN JOSE — A mega campus of office towers and retail spaces that would be the size of a major shopping mall is beginning to take shape in downtown San Jose across from the city’s convention center.

The campus, which would sprout on South Almaden Boulevard between the convention center and the Children’s Discovery Museum along the banks of the Guadalupe River, represents a fresh effort to tap the transit potential of the city’s urban core — and the rising interest of tech companies in the area.

The anticipated development from Boston Properties, a major real estate firm, would contain a total of as much as 2 million square feet of mixed-use offices and retail, and would feature two office towers, each 17 stories high, according to an environmental impact report on file with San Jose city planners.

“Higher, taller, and denser buildings are the right thing to do in a downtown core,” said Mark Ritchie, principal executive with San Jose-based Ritchie Commercial, a real estate firm. “That’s why downtowns exist.”

At roughly 2 million square feet, the development would be as large as, or even bigger than, major regional shopping centers in the Bay Area.

By comparison, the existing Westfield Valley Fair mall in San Jose is approximately 1.5 million square feet, although an ongoing expansion would take that complex to the 2 million-square-foot mark. Pleasanton’s Stoneridge Shopping Center totals 1.3 million square feet.

Boston Properties has sketched out two scenarios for the big new tech campus, which would consist of two office towers and ground-floor retail. CBRE brokers Sherman Chan, Jeff Houston, and Mike Benevento are seeking one or more tenants for the striking complex.

Under one plan, the development would include as much as 1.99 million square feet of offices and retail within two office towers. In this version, 1.95 million square feet of offices and 35,000 square feet of retail would be built, CBRE and Boston Properties said. That amount of office space could accommodate 9,000 workers.

A slightly smaller campus, totaling 1.46 million square feet, would emerge under a different proposed scenario. This version would consist of 1.42 million square feet of offices and 35,000 square feet of retail. About 6,500 office workers could be accommodated at the campus with this scenario.

“Ground floor amenity, food, and beverage space” would be the composition of the retail, the city planners stated.

In addition, a podium building would connect floors one through five of the two office towers.

The western edges of the buildings would each curve and follow the contours of the Guadalupe River. Open areas are envisioned for spaces between the buildings and near Woz Way, according to site layouts for the project.

The development is planned for the northwest corner of South Almaden Boulevard at Woz Way and Balbach Street.

These plans for a significant new tech campus in downtown San Jose arrive as big-time technology industry players have pushed ahead with efforts towards major expansions in the urban core of the Bay Area’s largest city.

San Jose-based Adobe has decided to embark on an expansion of its downtown headquarters campus that now consists of three office high rises by constructing a fourth office tower on an adjacent lot where 4,000 of the cloud services titan’s employees would work.

Near the Diridon train station and SAP Center, Mountain View-based Google has proposed a transit-oriented community of office buildings, homes, restaurants, shops and open spaces where 25,000 people could work, including 15,000 to 20,000 of the search giant’s workers.

Boston Properties also has jumped into another downtown San Jose project, the proposed Platform 16 office campus totaling 1.02 million square feet at 440 W. Julian St. next to Autumn Parkway that the company is developing in a joint venture with TMG Partners and Valley Oak Partners.

Among the notable projects developed by Boston Properties: The landmark Salesforce Tower in San Francisco.

“The reputation and track record of Boston Properties is stellar and this is the type of development downtown San Jose needs,” said Bob Staedler, principal executive with Silicon Valley Synergy, a planning consultancy.