The Senate Building, formerly known as the Judicial Annex, once housed the Ohio Supreme Court.
Completed in 1901 to house the Ohio Supreme Court, the former Judiciary Annex is now the Ohio Senate Building. Thirty-one of the thirty-three senators' offices are located in the Senate Building,
The Great Seal of the State of Ohio adorns the upper facade of the Senate Building.
along with conference and hearing rooms where members meet and deliberate. The offices of the Senate President and the Senate Minority Leader are located in the Statehouse.

Over the years, the building had deteriorated badly and a major restoration was undertaken in the 1990s to bring it back to its original Beaux Arts splendor. During renovation, fourteen coats of paint were removed to reveal the original wall colors, white marble, Columbus limestone, glass skylights, and intricate tile work. Though the Ohio Supreme Court now enjoys newly renovated facilities on Front Street, you can still see remnants of the Judiciary Annex era amid the Senate offices and hearing rooms.

Upon completion of the renovation in 1996, the Third Street entrance to the Senate Building was transformed into a memorial to honor Ohio's veterans. The Ohio Veterans Plaza is anchored by two curved limestone walls which feature inscriptions of letters written by and for members of the armed forces serving in conflicts. The fountains on each side of the Veterans Plaza offer visitors an atmosphere of quiet reflection. Lining the grassy area between the two walls are eighty-eight flag poles - one for each county in Ohio. Flags are flown on the poles to honor occasions of civic importance.
 
Two fountains in Veterans' Plaza honor the sacrifice made by Ohioans who have served in the military. Both are located outside the Senate Building.
On occasions of civic importance, 88 Ohio flags representing Ohio's 88 counties are flown in front of the Senate Building.
Two curved Ohio limestone walls stand at each end of the Veterans Plaza. The walls feature inscriptions of letters written to and from Ohio service men and women.