Not contradicting the references to the Darth Vader sculpture on The Washington National Cathedral in Washington I would like to direct you to two buildings in Spain.
Sagrada familia is a famous cathedral in Barcelona, Spain. The architect behind it is the late Antoni Gaudi. He is also the architect behind the building Casa Mila. Both buildings are equipped with sculptures/design elements which reminds the spectator about Star Wars storm troopers.
The blog Sistersbailey mentions that George Lucas was inspired by Gaudis Roman guards for his storm troopers. Many other webpages says things like "[..] it is said that George Lucas was inspired[..]", but I have not found a proper reference to this. In an age where Apple can copyright a telephone with rounded edges my guess is that Lucas wouldn't stand a chance in court.
Casa Mila Ventilation ventilation towers (Source Wikipedia)