The Mogao Grottoes, a world heritage site in northwest China's Gansu province, received a record one million visitors so far this year.

Bolstered by the weeklong National Day holiday, which ended on Oct. 7, the Mogao Grottoes in Dunhuang reached its highest number of annual visitors since opening in 1979.

The number of visitors hit the 6,000 daily limit every day for the past three months, Dunhuang Academy, which is in charge of the research, protection and management of the heritage site, said on Friday.

Increased traffic pushed the academy to raise the daily visitor limit on alternating days during the peak travel season. On some days, the number of visitors reached 10,000.

Tickets now must be reserved ahead of time.

The 1,600-year-old Mogao Grottoes, or the Ancient Caves of 1,000 Buddhas, became China's first UNESCO World Heritage site in 1987. It has more than 2,000 colored sculptures and 45,000 square meters of frescoes in more than 700 caves spreading 1,600 meters along a hill.