The Tower of London houses the Crown Jewels in the Jewel House, which is consistently the single busiest point inside the fortress, particularly in the late morning and early afternoon.
Head there first
Visiting the Jewel House shortly after the Tower opens, before the site fills up for the day, generally means a shorter wait than visiting it later.
The moving walkway keeps the line flowing
Inside the Jewel House, a moving walkway carries visitors past the jewels themselves, which keeps the queue moving steadily even when the room is busy, rather than allowing it to stall.
Yeoman Warder tours
Free guided tours led by the Yeoman Warders ("Beefeaters") run at regular intervals from just inside the entrance and are a good way to get oriented before exploring the rest of the site independently.

