FRANK LLOYD WRIGHT never designed just for the sake of designing. He wanted his ideas to be executed, to be built. And although he designed more than 1,000 landmarks of architecture, and although nearly 45 percent of those were constructed -- a very high percent as architectural commissions go -- the architect believed that his unbuilt designs were the most interesting of his works.

Wright's projects have remained unexecuted for reasons that range from the dramatic to the absurd. Bankers were frequent obstacles to construction, often fearful of Wright's large, soaring and controversial plans. The stock market crash of 1929 and World War II doomed other projects forever to the drawing board. But many of Wright's designs were not built because Wright himself consistently refused to compromise his work nd his principles. He preferred to see a project dropped and his drawings returned than to sacrifice beauty to please a client, a contractor or a building commissioner.

Such was the case with two local Wright might-have-beens: a planetarium that would have topped Sugarloaf Mountain, on the borders of Montgomery Crystal Heights, a massive project that Wright envisioned for Connecticut Avenue in downtown Washington.

The Crystal Heights project was set in motion in August of 1940 when Wright received a telegram from Roy S. Thurman, an enthusiastic and extremely likable young man charged with sense and vision and blessed with the recent purchase of a tract of land called Temple Heights in downtown Washington. Thurman's proposal called for a hotel of 1,000 rooms, plus residential apartments, along with shops, parking garages and a theater to seat 1,000 people.

Wright and Thurman met briefly in Milwaukee, and in a remarkably short time Wright worked up preliminary drawings and sent them to Thurman with a description of the project.

"The whole thing should be worked out in white marble, verdigris bronze and crystal," wrote Wright in the letter that accompanied the drawings, "and show up the Capitol for a fallen dumpling and Washington hotels as insufferable. And this is to suggest that you change Temple Heights to CRYSTAL HEIGHTS because of the crystalline character of the whole edifice. It will be an iridescent fabric with every surface showing of the finest quality."

Wright's letter and outline went on to discuss the number of rooms in the lavish hotels, the breakdown of apartments, the hotel banquet halls, the oak tree gardens, parking spaces, cocktail lounge, bowling alleys, cinema, gallery and museum that all would be part of the luxurious Crystal Heights.

"I have assumed that you wanted to make a clean sweep of the success of Crystal Heights," Wright said in closing, "and I am proceeding accordingly with a thoroughbred.

"After all, no half-way measures, or men either, are ever greatly successful. This calls for protective administration of what it has to give to Washington, and that ought to mean the world."

Throughout the summer and fall of 1940 the letters continued between the two men as the project was refined, estimated and planned down to each engineering detail. But by January of the following year, the beautiful Crystal Heights was defeated by a zoning law that forbade any tower higher than 110 feet, as well as by various civic groups in Washington who were horrified to see the Nation's Capital on the verge of constructing a modern building. It was finally killed off by the solemn conclusion that "any edifice that is not Greek, nor at least Colonial, is unfit for the Nation's capital." Mediocrity won, and the plans were returned to Wright and stored away.

IN 1925 a Chicago businessman, Gordon Strong, was eager to develop a tourist facility in and around Sugarloaf Mountain. Strong, who was attracted to the sense of engineering he saw in Wright's work, had begun to acquire property near Sugarloaf and recognized that motor touring was quickly becoming an American craze, along with hiking and horseback riding. The notion of state and national parks was gaining more and more appeal.

He and Wright dreamed that Sugarloaf Mountain would give the touring public the "Automobile Objective," an accessible height to which a car could travel and its passengers could enjoy overlooking the surrounding forests. The area would offer restaurants, cafes, shops and other amenities designed to attract the traveling tourist.

Within the great Automobile Objective itself was designed a planetarium. The outside reveals the landscape of the earth; the inside provides a landscape of the galaxies.

The project was abandoned shortly after it was designed. There was a heated exchange of letters between architect and client. Strong objected that the structure was not appropriate to the site; Wright defended his work on the grounds that it was perfectly appropriate to both site and circumstance.

Years later, in 1943, Wright finally succeeded in executing the spiral theme that he had planned for the Sugarloaf planetarium. But it is in New York's Guggenheim Museum that the spiral as a form for the structure both inside and outside finally came to be.