One's fondest memories are often those spent with like-minded people.

Xu Beihong (1895-1953), a pioneer of 20th-century Chinese art, would tell stories from time to time of a trip he took to Huangshan Mountain, in Anhui province, in April 1936. While there, he unexpectedly met two artist friends, Zhang Daqian (1899-1983) and Xie Zhiliu (1910-97). Together, they climbed the mountain, which is famous for its views of the clouds and oddly shaped rocks and pine trees. In memory of the trip, Zhang later created and engraved a seal with Chinese characters declaring, "Three incredible men atop Huangshan Mountain".

Zhang is today regarded as a giant of 20th-century art and someone with international prominence. When talking about his accomplishments, people often quote Xu, who said that Zhang was "a man once in 500 years" — meaning he was a gifted man comparable to the great artists in history.

The friendship between Xu and Zhang is preserved in the photos of their Huangshan trip and the paintings on which they collaborated throughout the years. These works are now on show at Between the Thousand Years, an ongoing exhibition at Beijing's Guardian Art Center.

The show, running through March 10, gathers paintings, calligraphic scrolls, manuscripts and documents, primarily from the collection of Xu Beihong Memorial Museum in the capital city, which houses a great number of Xu's works and his assembly of ancient art and selected works by his friends, including Zhang.

The exhibition also marks the close association between Xu and Qi Baishi (1864-1957), which is still talked about today. Despite an age gap of 30 years, Xu was one of the key figures who, in the late 1920s, introduced Qi, a humble carpenter-turned-painter, to the art scene of Beijing. Xu, who was a famed artist returning from Europe when they first met, helped launch Qi's career by enthusiastically promoting his works at home and abroad.