A most unusual experience indeed !
Tunnels are mentioned rather frequently by people who have had OBEs. As you may be aware tunnels are mentioned most often by people who have had Near Death Experiences. However, people who have OBEs also report tunnels as well.
Most often though people who OBE report portals or gates that usually go to another location or another dimension/plane.
My own belief is that tunnels and portals are both Stargates (variously called wormholes, Kerr Tunnels or Einstein-Rosen Bridges). These stargates connect different locations throughout our 4 dminesional space-time continuum and also lead to other, alternate universes. [

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