The Brownstone is a house located in New York City at 42 Stanford Avenue, Brooklyn, New York, 11209. ("We Are Everyone") It is home to Sherlock Holmes and Joan Watson and was owned by Sherlock's father Morland until willed to Sherlock. ("The Visions of Norman P. Horowitz") The house consists of at least four floors, including a basement, and a terrace on the roof. The roof has a view of Queensboro Bridge and Manhattan, and is also where Sherlock keeps his bees.
Watson establishes an office in the basement and initially, nails the inside door shut so that that it is only accessible by the outside door. ("When Your Number's Up") Holmes helps himself to Watson's office and stores items in the basement such as his "box of swords". ("The Adventures of Ersatz Sobekneferu") There's also a motorcycle stored under the stairs.
The library and several work rooms are on the first floor.
Although the Brownstone is in Brooklyn on the show, the outside of the building is shot in Harlem, New York City, with interiors shot at Silvercup Studios in Queens. The roof is a real rooftop in New York City and is located on a parking garage at the corner of 10th St & 44th Av.
The Brownstone is also seen on W 121st Street (near the intersection with Malcolm X Blvd), just around the corner from "Owens Funeral Home" in Harlem. ("Wrong Side of the Road")