The O2 Arena is vast, offering room for around twenty three thousand revellers depending on what’s on stage. There’s a flat floor plus two tiers, the first of which covers areas 101 to 112 and the second areas 401 - 422.
In the main arena, central floor seating comes with enough legroom and good views of the stage, surrounded by the steep banks of the lower-tier seating with their private boxes. The closer the boxes are to the stage, the better the views, with great visuals and sound.
The arena seats are on a relatively shallow slope so you might encounter people’s heads in the way in front of you. But the issue doesn’t occur when events are staged centrally, as they often are. The lower tier seats are steeply sloped with good views all round even at the sides. The upper tier seating is very steep indeed and not for the faint hearted! And the balconies, while giving decent views, have safety rails which can get in the way.
Bear in mind the seating at the O2 changes depending on the event.