Vlastimil Koubek was the architect for the East Building (L'Enfant Plaza Hotel, located at 480 L'Enfant Plaza SW), and for the Center Building (475 L'Enfant Plaza SW; now the United States Postal Service headquarters).
Vlastimil Koubek menjadi arsitek Gedung Timur (L'Enfant Plaza Hotel, terletak di 480 L'Enfant Plaza SW), serta Gedung Tengah (475 L'Enfant Plaza SW; sekarang markas besar United States Postal Service).