A cycle of five lands that produce two types of mana were printed in Scars of Mirrodin with a static ability that replaces how they enter play. Blackcleave Cliffs would be an example of one of these lands. The gist of it is that they enter play untapped as long as you don’t control that many other lands. So very early game they are great, they are not as good late in the game.

Specifically, they enter play untapped as long as you control two of fewer lands as they would enter play. In other words, these lands enter play untapped as long as they are the first, second or third land you play. If for some reason, one of these lands and at least one other land were to center the battlefield at the same time under your control, you do not count the lands that are coming at the same time as this Scars ‘tap land.’