Lorimer Rich, 86, the architect who designed the Tomb of the Unknown Soldier, died Friday in a nursing home in Rome, N.Y.

He had been transferred to the home on Thursday from a Rome hospital, where he had been a patient for several weeks. The cause of death was not disclosed, the Associated Press reported.

The Amphitheater in Arlington Cemetery was completed in 1920. An unknown soldier of World War I was buried there on Armistice Day in 1921 but the tomb that now contains his remains was not added in front of the theater's east portal until 1931.

Two years earlier, a national competition had been held for design of the tomb. Mr. Rich's design won out over 70 other plans that had been submitted.

The large marble sarcophagus has Doric pilasters at the corners and sides, giving the monument the appearance of a miniature Greek temple. Three graceful figures in flowing Greek robes stand in the temple door.

There is an inscription: "Here rests in honored glory an American soldier known but to God."

Flat stones marking the crypts of unknown soldiers of World War II and Korea flank the tomb.

Mr. Rich, who was born in Camden, N.Y., where he lived in later years, was a graduate of Syracuse University. He studied classical architecture at the American Academy in Rome.

As a young man, he worked for architects McKim, Mead and White and participated in the design of a number of government buildings in Washington and elsewhere. He was architect for a number of colleges.

Mr. Rich practiced in New York City and had been a member of the New York State Board of Architect Examiners. He was a fellow of the American Institute of Architects.

He is survived by his wife and a daughter.