Portals

Publisher's blurb:

The Dungeon Feature series is designed to help you come up with details for features found in dungeons*. This particular volume covers Portals.

A portal is, in many ways, like a door. They both take you to another place once you step through it. The main difference between a door and a portal is that a door takes you to the next chamber, corridor or even outside.

Stepping through an active portal however and you may find yourself on the other side of town, in another country, or maybe even the other side of the world. Some portals can take you even further, to other worlds, star systems or even universes/planes of existence...