In the autumn of 1953, the Central Committee decided to work at the seaside resort of Beidaihe every summer. In practice, the arrangement was “half rest and half work.” Formal meetings were held there too, such as the enlarged Politburo meeting of August 1958. The summer office continued until 2002, with a break during the Cultural Revolution. It was abolished soon after Hu Jintao became general secretary.
According to Chinese Wikipedia, gatherings and even informal meetings still took place at Beidaihe in summer after 2012.