Construction crews from John Moriarty Assoc. placed the final beam atop the $250-million, 38-story Avalon North Station apartment tower scheduled to open in late 2016.

The CBT Architects-designed structure will contain 503 apartments ranging from studios to three-bedroom units, a fitness center, wifi café and lounge, meeting and communal workspace, a bike repair shop and sky lounge and rooftop terrace on the 35th floor. A two-story arcade will provide a pedestrian connection between Nashua and Causeway streets.

“Avalon North Station is a celebration of smart-growth, sustainable design and contemporary urban living,” Scott Dale, AvalonBay’s senior vice president for development, said in a statement. “These new apartment homes will help in the transformation of the North Station area and are yet another example of our commitment to the city of Boston.”

The complex is part of a massive development boom in the West End, North Station and Government Center neighborhoods. Nearly 8 million square feet of residential and commercial buildings are expected to be completed in the next few years. Boston Properties broke ground last month on the first commercial building in its $1 billion North Station redevelopment. Boston-based HYM Investments is seeking final design approval for a 486-unit apartment building and 1-million-square-foot office tower in the first phase of its $2.2 billion Government Center garage redevelopment.