This may be Christie’s biggest jewelry auction yet—and perhaps one of the largest in history.

Over 700 dazzling high jewelry pieces belonging to Austrian billionaire Heidi Horten, who died last year at 81, are part of the sale series dubbed The World of Heidi Horten.

Horten, a philanthropist known for her elegant taste, amassed over the course of her lifetime one of the world’s most brilliant jewelry collections. Highlights include a 90-carat Briolette of India diamond necklace by Harry Winston, originally sold by Cartier in 1909; a cushion-shaped, brilliantly cut 25-carat ruby and diamond ring by Cartier; and an exceptional collection of notable Bulgari jewels.

The pieces are expected to fetch a record-breaking $150 million. Part one of the live auction took place earlier today at the Four Seasons Hotel des Bergues in Geneva, while part two of the live auction is set for May 12, with online bidding continuing through May 15.

Per Horton’s wishes, the Estate’s proceeds will  benefit The Heidi Horten Foundation, which supports Horten’s Vienna-based art museum as well as medical research, child welfare, and other philanthropic activities that she supported.