The Palace Museum in Beijing, also known as the Forbidden City, on Wednesday unveiled plans to control the number of visitors for the purpose of protecting the former imperial palace, a UNESCO World Heritage Site.

The plans, including not allowing annual ticket holders to visit during peak seasons, a seven-day promotion of ticket sales for afternoon visits from July to August, and online pre-sale of tickets during festivals and holidays, were announced at a public hearing.

The museum will also set two days for free visits during off seasons, when fewer than 80,000 visitors are allowed to obtain tickets via online channels.

Shan Jixiang, the museum curator, said management had been looking to find ways to control the number of visitors while at the same time better protect its cultural relics and serve the public.

A comprehensive plan to better preserve the Palace Museum approved by the State Council, China's cabinet, states that it will be built into a first-class museum by 2020, when the former imperial palace will celebrate its 600th anniversary.

Major projects under the plan include remolding underground storehouses, restoring cultural relics and rebuilding infrastructure.

In an effort to renovate the Imperial Garden, located near the northern gate of the Forbidden City, museum authorities have banned the sale of snacks, removed some of the railings and opened two tourist centers, Shan said.

The museum had been closed on Monday afternoons since January 2013. The closure was extended to cover the whole of Monday for renovation and maintenance from Jan. 6 this year.

In the heart of Beijing, the Forbidden City was home to China's emperors in the Ming and Qing dynasties and was the highest center of power for about 500 years. It attracts more than 14 million visitors annually.