A prime undeveloped parcel next to the future General Electric headquarters is on the market as Gillette tests the value of its sprawling South Boston campus.

JLL Boston is marketing the 6.5-acre surface parking lots overlooking Fort Point Channel, one of the last unclaimed development sites in the sought-after Seaport District.

A spokeswoman for Gillette parent Procter & Gamble told the Boston Globe that the recent sales of two smaller sections of the 40-acre campus encouraged the razor-maker to place additional real estate on the market.

Fully permitted parcels in the Seaport District have sold for more than $30 million per acre in recent years, including Cottonwood Group’s $120 million acquisition of 3.5 acres in 2015 for its 1.3-million EchelonSeaport residential and retail complex.

Newton-based WS Development paid nearly $29 million per acre for a 12.5-acre portion of the master-planned Seaport Square, where it’s approved for 7.7 million square feet of development including a 525,000-square-foot building leased to Amazon.