Massport is offering up more of its Seaport District real estate for a project that could encompass up to 600,000 square feet of development while improving the MBTA’s Silver Line Way stop’s visibility and accessibility.

The Parcel H site next to 601 Congress St. contains 1.1 acres of undeveloped land and an option for another 1.4 acres of air rights on Silver Line Way.

In a request for proposals issued Thursday, Massport said it’s looking for a “mixed-use commercial” development that could such uses as offices, lab space, a hotel, housing or some combination thereof.

Massport said it’s seeking proposals with “significant” contributions to the public realm such as “inspired architecture, creative programming and placemaking” to serve the general public, along with improvements to the MBTA Silver Line Way station. Suggested improvements to the existing dedicated busway stop include a “prominent entrance” and vehicle drop-off spot on Congress Street and possible access from Starboard Way, and two, 200-foot-long boarding areas.

The site’s maximum parking component is 200 spaces, with additional parking available at the Massport waterfront transportation center garage.

The agency also wants developers to include minority- and women-owned businesses in all aspects of the project including design, ownership, construction and operations.

Proposals are due Sept. 27.