In gentrifying Brooklyn, as neighborhoods shift, once booming businesses can fade away.

But at District, a new gym inside the former Scotto Funeral Home in Carroll Gardens, there’s hope in the afterlife.

Carved out of the combined lower floors of two stately brownstones on a tree-lined block, the 3,500-square-foot gym replaced what for decades had been dimly lit chapels, a casket showroom and a smoking lounge for the bereaved.