Preservation

This spell creates a powerful set of protective wards that operate on a single fortified building, temple complex, tower, or similar structure. These wards protect the physical integrity of the structure and prevent magical access.
A building protected by preservation suffers only 25% of normal structural damage from sources such as siege engines, earthquakes (both natural and magical), and powerful weather-affecting spells. Spells which directly affect the physical integrity of the structure (e.g., Passwall, stone shape, transmute rock to mud) simply fail when cast on the protected building.
Preservation creates a permanent protection from evil spell on the affected building. Every surface of the building benefits from the effects of the spell.
Magical spells allowing access to the building fail. Thus, creatures attempting to Teleport or Fly into the building are stopped. Birds and creatures with natural flight may enter the building normally.
If the building is a temple (or other consecrated building) dedicated to the deity that granted the spell, all priests inside it gain the benefit of a Sanctuary spell for the duration of the preservation.
The preservation spell expires if the building is destroyed or after 60 days have passed.

[Tome of Magic]

Sphere: Wards
(Abjuration)
Quest

Range: 480 yards
Components: V, S
Duration: Special
Casting Time: 1 turn
Area of Effect: One structure
Saving Throw: None