Where am I?

Bob was driving to work when a truck ran a stop sign, hit his car broadside, and knocked him cold. Passers by pulled him from the wreck and revived him.

Bob began a terrific struggle and had to be tranquilized by the medics.

Later, when Bob was calm, they asked him why he struggled so.

Bob said, "I remembered the impact, then nothing. I woke up on a concrete slab in front of a huge, flashing sign. Turns out somebody was standing in front of the ’S’ on the ’Shell’ sign.