A drawing of the proposed Eldridge expansion.

Downtown Lawrence’s venerable Eldridge Hotel is set to get a modern, multi-story expansion.

Architects for the Eldridge, 701 Mass., have submitted plans to City Hall for a four-story expansion on the vacant lot immediately south of the historic hotel.

And Quantrill — who once razed the Eldridge — wouldn’t recognize this one. Plans call for parts of the building to feature a retractable roof and large glass storefronts that swing completely open to create an outdoor café setting.

“We’re pretty proud of some of the features,” said Paul Werner, a Lawrence-based architect who is designing the project. “It definitely will be a bit more modern than the Eldridge.”

Other details include:

• The first and second floors — about 11,000 square feet total — would house restaurant, bar and banquet space.

• The third and fourth stories would include 16 new hotel rooms for the Eldridge, which currently has 48 suites.

• A new elevator to serve both the new and existing parts of the hotel would be constructed.

Werner said the new dining and banquet space likely would accommodate 300 to 400 people. The restaurant — dubbed Nine at the Eldridge — would be an extension of the hotel’s current Ten restaurant.

The restaurant would feature ground floor dining that would open up to Massachusetts Street when the two 15-foot wide glass storefronts are swung open. It also would include second-floor mezzanine dining space beneath the retractable roofs.

“This is the type of space that can attract new events to downtown,” Werner said.

The hotel’s development group — which includes members of Lawrence’s Fritzel family — hopes to start construction this fall.

The project is seeking final approval from the city’s Historic Resources Commission on Sept. 16.

Lynne Braddock Zollner, the city’s historic resources administrator, said the project thus far is moving through the process well.

“I think it is coming together great,” Zollner said. “It has a little bit of a modern flair, but it is respectful of the Eldridge and the spaces around it.”