A revolving bookshelf leads to an underground passage in this Lloyd Harbor house, listed for $4.1 million.

The tunnel, about 100 feet long, connects to the detached garage, says Paul Tyree of Laffey Fine Homes International, the listing agent for the home.

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"The entire home is built on one big hill, so instead of having room for the garage on a lower part of the property, this was the only way the previous owner felt was possible to have access to the garage," Tyree says.

The five-bedroom, four-bathroom, and a half-bath house has been updated and renovated within the past four years.

It has a sauna, spa and theater in the basement, along with a 1,100-bottle wine cellar that has a self-controlled cooling system.

The home comes with a 400-foot pier and a 200-foot private beach.

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"This is one of the largest private docks in all of Long Island," Tyree says.