Newton-based National Development has begun $20 million in renovations to its 8-acre Constitution Wharf office property in Charlestown to coincide with the late summer arrival of Shoes.com, which has leased 31,300 square feet.

The 180,000-square-foot office property on a pier overlooking Boston Harbor was previously known as Constitution Center. It will receive a new double-height lobby, lounge, cafe and fitness area. Exterior improvements will include an outdoor “living room” with fire pit, media screen and event space.

Shoes.com will relocate from 101 Arch St. in Boston late this summer.

Newmark Knight Frank Executive Managing Director David Townsend and Senior Managing Director Tim Bianchi advised National Development in the transaction. John Butterworth and Nick Amarante of CBRE/New England represented shoes.com.

Several companies have submitted proposals for the remaining 70,000 square feet of availability in the complex, Townsend said.

Perkins & Will is providing the architectural services for the renovation, which also will include new covered bike storage, signs and public art.