While most attractions in Beijing allow entry without reservations, some popular sites still require advance booking.

For instance, the Forbidden City (Palace Museum) and the National Museum of China require reservations up to 7 days ahead, with tickets often selling out quickly. 

Tiananmen Square reservations can be made 1 to 9 days in advance, while the Tiananmen Gate Tower requires booking 1 to 7 days ahead. 

The Chairman Mao Memorial Hall allows reservations 1 to 6 days in advance, and the Great Hall of the People requires booking 1 to 3 days prior. For the Military Museum, tickets can be reserved up to 8 days in advance.