Abjuration
Level: Cleric 8, Sorcerer 8, Wizard 8, Urban Druid 8
Components: V, S
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Area: 20-ft. radius emanation centred on a point in space
Duration: 1 day/level
Saving Throw: None
Spell Resistance: Yes
You create a shimmering emerald barrier that completely blocks extra-dimensional travel. Forms of movement barred include astral projection, blink, dimension door, ethereal jaunt, etherealness, gate, maze, plane shift, shadow walk, teleport and similar spell-like or psionic abilities. Once dimensional lock is in place, extra-dimensional travel into or out of the area is not possible.
A dimensional lock does not interfere with the movement of creatures already in ethereal or astral form when the spell is cast, nor does it block extra-dimensional perception or attack forms, such as a basilisk’s gaze. Also, the spell does not prevent summoned creatures from disappearing at the end of a summoning spell.
Source: Player’s Handbook (Page 221)