Frei Otto

BERLIN (AP) — Architect and engineer Frei Otto, who pioneered lightweight and flowing roof designs for stadia and other structures and was to receive this year's prestigious Pritzker Prize, has died in his native Germany. He was 89.

Ingrid Otto, who lived with her husband in Leonberg near Stuttgart, told the dpa news agency Wednesday that he died on Monday, two months before his 90th birthday.

Otto had been informed he'd won the 2015 Pritzker Architecture Prize, but the official announcement wasn't due until later this month.

Best known for the roofing of the Munich Olympic Park and the German pavilion at the 1967 Expo in Montreal, the prize citation called his work "lightweight, open to nature and natural light, non-hierarchical, democratic, low-cost, energy-efficient, and sometimes designed to be temporary."