A historic Brooklyn waterfront townhouse has gone on the market for $9.99 million.

The Brooklyn Heights home, known as the Captain’s House, is located at 13 Cranberry St., just steps from the Brooklyn Boardwalk.

Built in 1829 by Richard Mortimer, a British captain, the 25-foot-wide house was recently renovated by Baxt Ingui Architects.

The three-story, 4,900 square foot home features five bedrooms and 3½ bathrooms.

The house is also home to a secret – a hidden cavity inside a post, where Captain Mortimer is said to have hidden the deed to the house almost 200 years ago.

It’s apparently an old British tradition, depending on the brokerage firm selling the property.

After the mortgage was fully paid, the landlord apparently drilled a hole in the post and placed the wrapped mortgage document inside, then sealed the hole with a decorative wax seal.

Design details include crown molding – intricate fruit patterns that nod to the fruit streets of Brooklyn Heights – as well as two fireplaces, 11-foot ceilings, the original staircase and plenty of storage. .

There are also heated floors inside the house as well as a heated front porch and sidewalk outside.

The house opens onto an entrance hall. It faces a row of gardens across the street as well as a row of gardens to the rear.

There is also a chef’s kitchen with white cabinets and white marble countertops. The second level is the owners’ suite, with a fireplace and spa-like bathroom, two walk-in closets, and a “bonus” room that can be a home office, living room, or bedroom.

The upper floor has a laundry room and two more bedrooms, with fireplaces and large closets. The upper level of the attic could be another office or living room.

The broker is “Million Dollar Listing New York” star Tyler Whitman of Triplemint.