See Beijing's icons without turning the trip into a forced march.

Temple of Heaven in the morning for locals doing exercise, hutong walking and snacks midday, Peking duck dinner. Keep jet lag in mind if you just landed.
Tiananmen Square logistics, Forbidden City with a smart route, Jingshan Park viewpoint for the classic palace rooftop photo. Do not underestimate walking distances inside the palace complex.
Full wall day. Return tired but happy. If you have a fourth day, add Summer Palace or 798 art district instead of compressing more into day 2.
Ticket timing, palace routing, wall logistics, and dinner reservations or local restaurant picks. Beijing rewards good sequencing.
Enough for highlights, not for everything. Prioritize wall + palace + one neighborhood day.