Though all the buildings are beautiful -which building is the most beautifully constructed stone building amongst them all at the Washington...

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.