Though all the buildings are beautiful -which building is the most beautifully constructed stone building amongst them all at the Washington National Cathedral?
Your question is somewhat confusing in that it seems to imply that there are several special, beautiful stone buildings at the site of the National Cathedral. To my understanding, the Cathedral itself is the only major architectural structure on site.
Perhaps you are asking about the National Cathedral in comparison to structures elsewhere in the world.
The Washington National Cathedral, located in Washington, D.C., is a Neo-Gothic or Gothic Revival structure, the construction of which began in 1907, with completion 93 years later on the addition of the last finial in 1990. It is the third most popular structure in the United States, standing behind the Empire State Building and the White House.
In terms of stone buildings of architectural magnificence, cathedrals dominate. There are no structures with greater detail and beauty. Therefore, the Washington National Cathedral must be compared to other cathedrals throughout the world.
The Washington National Cathedral is the 6th larges cathedral in the world, but not among the top ten in terms of architectural splendor. Famous cathedrals that share a higher position in architectural rating would include Notre Dame Cathedral in Paris, France, St. Peter’s Basilica in the Vatican, Rome, Italy, St. Joseph’s Oratory of Mount Royal in Montreal, Quebec, Canada, and the Guadalajara Cathedral in Guadalajara, Jalisco, Mexico.
In the United States a cathedral that rivals the National Cathedral is the French Gothic Cathedral Basilica of the Sacred Heart located in Newark, New Jersey.