This spring, the Asian market for ancient Chinese artworks, which languished during the worldwide recession, rebounded dramatically, with numerous lots setting new records. However, amid all of that action, one set of lots, sold from the Guy & Myriam Ullens Collection at Beijing Poly International Auction Co., Ltd. last month, stood out. All 12 lots on offer from that collection — an assortment of works by ancient and modern Chinese artists, including seven antiquities that were exhibited at Beijing's Palace Museum in 2002 — sold, fetching RMB 146.2 million ($21.4 million).

The success of the auction was not entirely unexpected, considering that the Ullenses — a Belgian couple who started collecting rare ancient Chinese artworks in the 1980s and founded the nonprofit Ullens Center for Contemporary Art in 2007 in Beijing — are among the most prominent collectors of Chinese art worldwide. Last year, in Poly's fall sale, the Ullens' two lots — Ming court painter Wu Bin's 1615 Portraits of Eighteen Arhats (which the couple purchased in 1992 for only $620,000) and Letter Leaf by scholar Zeng Gong, who is considered one of eight greats of the Tang and Song dynasties — were respectively sold for RMB 16.9 million ($24.7 million) and RMB 10.8 million ($15.8 million), breaking records in ancient Chinese painting and calligraphy.

While questions about the Wu Bin work's attribution were raised by some Chinese art collectors before the painting headed to China, it was later authenticated by Poly auction specialists based on an inscription in the distinctive handwriting of Qing dynasty Emperor Qianlong, who was known for his connoisseurship.

Ambitious collectors and the newly-moneyed class in China are awaiting the next surprise from the Ullenses, who own an unknown amount of rare classical works.