They can only be seen from Tiananmen Square, where you need to pre-register. In general, there are a lot of hemorrhoids, not to say that it's worth it. But this is a significant place, in principle, it's worth taking a look once.
The Gate of the Heavenly World is the main entrance from Tiananmen Square to the Forbidden City. You will have to wait here because of additional security checks. The impressive building had great historical and symbolic significance back in the time of the Chinese emperors, as well as for the Communists under Mao Zedong, and therefore it is a must-visit while in Beijing.