Rock Ridge Culvert

Location

This area is underground of Rock Ridge and is not a dungeon, thus can be memorized with Acolyte's Warp Portal.
There are 2 ways to enter (must be lvl 100+ for NPCs to allow you through):

1. Talk to Joe harboro1324124 at the east side of Rock Ridge, on top of stairs of a house to enter.

   

2. Talk to Underground Passage harboro1335144 that is near Joe, under a water tower to enter.

   

Escape

There are 2 ways to exit:

1. Talk to Underground Passage harboro2331187 at the northeast side of the map.
   

   

2. Enter the portal harboro2283104 at southeast side of the map.