Conjure Fortification is a Daily power given to Wizards at 6th level[HotEC]
Conjure Fortification
Wizard Utility 6
A low stone wall rises from the ground, offering cover against attack or passage over an obstacle.
Daily ✦ arcane, conjuration
Area wall 5 within 10 squares
Effect: You conjure a wall of stone. The wall can be up to 1 square high, and at least 2 squares of it must rest on a solid surface. The wall lasts until the end of the encounter. The wall is blocking terrain. A creature can climb the wall with a DC 15 Athletics check.