Question: What building did Alexander Blair III design in the city nicknamed "the Heart of Georgia"?

Context paragraphs:
Decatur County Courthouse (Bainbridge, Georgia): Decatur County Courthouse is a historic county courthouse in Bainbridge, Georgia, the county seat of Decatur County, Georgia.  The Neoclassical building was designed by Alexander Blair III and built in 1902.  It was added to the National Register of Historic Places on September 18, 1980.  It is located on West Street and Water Street.

Alexander Blair: Alexander Blair III (April 22, 1867–November 16, 1931) was an American architect.  He designed the Grand Opera House (1884) in Macon, Georgia, eight Georgia county courthouses, and other buildings.  His father was also an architect and his son Algernon Blair (1873-1952) was a prominent builder.

Blair Historic District: The Blair Historic District is a historic district located in downtown Belleville, Illinois.  The district encompasses a mainly commercial area on the west side of the downtown area; it includes 78 buildings, 57 of which are contributing buildings.  The entire district is located within the original plat of the city, which was established following a land donation from George Blair in 1813.  The oldest buildings in the district date to circa 1850; development continued from then on into the early twentieth century.  Most buildings in the district are two-part brick commercial blocks designed in popular contemporary styles such as the Italianate, Second Empire, Classical Revival, and Romanesque Revival.  The Reichert Business Block, a three-story structure at 200 West Main Street, has a particularly significant Second Empire design; the building features a mansard roof with dormers and a decorative cornice and has been described as the district's most elaborate building.  Two Classical Revival buildings, the 1911 United States Post Office Building and the 1924 Turner Hall, also have a commanding presence in the district; the post office was designed by Supervising Architect James Knox Taylor.

John Blair (rugby player): John Alexander Blair (c.1871 – 12 April 1911) was a New Zealand rugby union player who represented the All Blacks in 1897.  His position of choice was hooker.  Blair did not play in any test matches as New Zealand did not play their first until 1903.

Ezell Blair Jr.: Jibreel Khazan (born Ezell Alexander Blair Jr.; October 18, 1941) is a civil rights activist who is best known as a member of the Greensboro Four; a group of African American college students who, on February 1, 1960, sat down at a segregated Woolworth's lunch counter in downtown Greensboro, North Carolina challenging the store's policy of denying service to non-white customers.  The protests, and the subsequent events were major milestone in the Civil Rights Movement.

DFW R.III: The DFW R.III was a German bomber aircraft designed during World War I, but which had not yet been built when the end of the war led to the project's cancellation.  Conceptually similar to DFW's preceding R.I and R.II designs, the R.III was to have been a much larger aircraft, powered by eight engines.  As with the previous designs, these were to be housed inside the fuselage, driving propellers by long driveshafts.  In the R.III design, however, these propellers were to be mounted on a nacelle in the interplane gap.  Each end of this nacelle would carry two co-axial propellers, each driven by a separate engine.  Had it been built, the R.III would have been the largest aircraft in the world at the time.

Appoline Alexander Blair: Appoline Agatha Alexander Blair (September 14, 1828 – Sep. 5, 1908) was a Missouri philanthropist, hospital founder, and wife of Senator (and Civil War general) Francis Preston Blair, Jr. In 1878, after losing two children to illness, Blair gathered a group of 20 prominent women and organized the St. Louis Children's Hospital, for which she served as the first president of the Board of Managers.  In addition to the St. Louis Children's Hospital, she is sometimes credited with the creation of the St. John's Medical Center in Joplin, Missouri, in 1896.

Alexander Blair (writer): Alexander Blair (1782–1878) was an English writer and academic.  Considered as an original thinker, he is also described as "disorganised, despondent and a ditherer".  He is known as a friend of Christopher North.

Macon, Georgia: Macon (officially Macon–Bibb County) is a city located in the state of Georgia, United States.  Macon lies near the geographic center of the state, approximately 85 mi south of Atlanta, hence the city's nickname "the Heart of Georgia."

Turner County Courthouse: Turner County Courthouse is a historic county courthouse in Ashburn, Georgia, the county seat of Turner County, Georgia.  The Classical Revival building was designed by two Macon architects, Alexander Blair III (who also designed seven other Georgia courthouses) and Peter E. Dennis.  The courthouse is located at 219 East College Avenue, close to several historic homes.

Supporting paragraphs: Alexander Blair Macon, Georgia
Answer: Grand Opera House