Crews building the Rodin Square apartment and shopping complex near the Philadelphia Museum of Art have laid the final beam of the project's frame, a milestone for one of the more prominent developments in an increasingly upscale section of the city.

The 10-story building's "topping-off," marked in a ceremony Tuesday, puts the $160 million project being developed at 501 N. 21st St. by Philadelphia's Rodin Group and Washington-based Dalian Development on track for completion in the summer.

It's the latest step in the transformation of the neighborhood along Benjamin Franklin Parkway from a quiet district of rowhouses and mid-range apartments among museums and parks into an increasingly bustling - and affluent - extension of Center City's core.

"This building is a new icon for the city, filling in a gap along the Parkway," Brady Nolan, Dalian's vice president for development, said at the ceremony. "It really is just a special project."

Rodin Square joins a wave of high-end apartment projects near the border between the Fairmount and Logan Square neighborhoods.

To the east, Cleveland-based Forest City Enterprises is adding a new 270-unit apartment building and 16 rental townhouses to its Museum Towers development near 18th and Spring Garden Streets. The expansion is on track to open in early fall 2016, spokesman Jonathan Gertman said.

Meanwhile, Denver's Aimco is renovating the mid-century Park Towne Place Apartment Homes at 2200 Benjamin Franklin Parkway to appeal to more contemporary tastes.

Aimco expects to complete work on the first of the four towers in January, after spending about $60 million on upgrades to the 230-unit building, senior vice president Patti Shwayder said.

Activity in the neighborhood comes as it attracts ever-higher-income residents. Average income in the area bounded by Spring Garden, Broad and Vine Streets and the Schuylkill rose 33 percent, to $91,960, from 2009 to 2013, according to U.S. Census data. Citywide, average income rose 6.5 percent, to $54,367, over that period.

The growing interest from developers also comes amid an influx of shops and restaurants to complement the area's cultural attractions and open spaces, said Philadelphia real estate agent Michael Garden.

The Whole Foods market at 2001 Pennsylvania Ave. was a boon to the neighborhood, he said, as are the burgeoning restaurants on Spring Garden and Callowhill Streets.

"What's been lacking in that area is a sense of walkability and enough amenities to attract people," Garden said. "But those amenities have been accelerating."

Rodin Square will further that trend, with the addition of an even bigger Whole Foods among its 85,000 square feet of retail space, to replace the Pennsylvania Avenue store. It will be the chain's largest location in the city and the only one with a restaurant-bar, said Scott Allshouse, Whole Foods' mid-Atlantic regional president.

Dalian on the Park, the project's residential portion, will accommodate 293 apartments with floor-to-ceiling windows, offering views of the area's expansive open space, museum architecture, and statuary.

"You have the museums, you have the Parkway," developer Neal Rodin said in an interview. "You have that suburban, grassy feel, yet you're 10 minutes from the center of the city."