"The great thing," counsels the distinguished Welsh architect and environmentalist Sir Clough Williams-Ellis, "is to start very young and live long enough to be very old and see the results."

Sir Clough's own accomplishments have been so diverse that he titled his autobiography Architect Errant. Yet none of his projects has been more remarkable—or eccentric—than his creation of the North Wales seaside resort of Portmeirion. Last month Sir Clough and his wife of more than six decades, 83-year-old Lady Amabel, presided at two days of festivities marking Portmeirion's 50th anniversary—and Sir Clough's 94th birthday.

On a craggy peninsula 240 miles from London, Sir Clough has created a fantasy village out of a hodgepodge of architectural styles: classical colonnades, terraced gardens, cobbled square and sleek bell tower. Set in 3,000 acres of otherwise gray landscape, Sir Clough's whimsy has evolved into a noted tourist attraction. It has been favored by the international literati such as Bertrand Russell, who stayed two years producing Freedom and Organization, and H.G. Wells, George Bernard Shaw, John Steinbeck and Thor Heyerdahl.

Sir Clough is known to friends as "the magpie of the world," and he himself admits Portmeirion is "the home for fallen buildings."

For it, he collected architectural fragments from all over—a bit of the 12th century castle of Gerald the Welshman, a statue from Aberdeen, a Jacobean ceiling for the town hall and a Palladian colonnade from Bristol for the town square.

"I'd never foreseen when I started here that we'd ever have an assembly like this," Sir Clough told the anniversary party. "Portmeirion has grown up." The government's Department of the Environment, which watches over the village, apparently did not foresee it either. "We had the jubilee celebration 10 years ago," Sir Clough chuckles. "The trustees didn't trust me to show up for the 50th anniversary, but here I am. I've outwitted them."

Sir Clough was an energetic host at the celebration. He and Lady Amabel, a well-known author, endured a cocktail party and dinner, then whirled through a masked ball that lasted beyond midnight. The next morning they were up for the day-long carnival. Twice a week Sir Clough reviews the list of 160 guests usually lodged at Portmeirion. "If we like them," he says, "we invite them home." One so honored in 1941 was Noel Coward, who dashed off Blithe Spirit in six days at Portmeirion.

Home for Sir Clough is his 17th century Plâs Brondanw (Plâs means manor house in Welsh, a language Sir Clough has never learned to speak). He has rebuilt the mansion twice and designed the gardens, including a topiary in the shape of two swans flying together. His ultimate refuge is his study—"a jolly explosion of notions"—and there Sir Clough is finally at rest. "My abiding nightmare has been that some takeover-tycoon would come and blow up the elegant little mouse that I designed into some unwieldy cow. But now that Portmeirion is protected, I shall depart this earth perfectly happy."