When you first start towers, you always have to go down to get to the next level. However, in the Crystalline Queen tower, for example, you go UP to get to the next level. If you aren't paying attention and go DOWN, you leave the tower and have to start the whole thing over because the rules for towers aren't the same as rules for other instances and you can't go back in or port in. I think that all towers in a world should be going one way or the other, either UP or DOWN. You could make the argument that if the tower goes up, it should go up, and if it's a dungeon down, but really, very few people pay attention to that. Uniformity would really improve my happiness in the game, and many other people's I'm sure.