Portal Sensitive

(Underdark, page 27, DnD 3.5)

[General]

You can perceive a portal just by passing near it.

Prerequisite

Deep Imaskar or gloaming

Benefit

You can detect an active or inactive portal as if it were a normal secret door (Search DC 20). If you merely pass within 5 feet of a portal, you are entitled to a Search check to notice it as if you were actively looking for it. You also gain a +2 bonus on your caster level check when trying to discern portal properties with the analyze portal spell.

Normal

Portals can be found only by using analyze portal, detect magic, or the granted power from the Portal domain