Jesus was crucified outside of the city as a sign of the world’s rejection of Him.  We go out to Him, not just to bear His rejection, but in order to be sacrificed there with Him.  He suffered there to make us holy.  Receiving that sacrifice by the sacrifice of ourselves brings us to this holy relationship.  It is there that you “present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship” (Rom 12:1).  To belong entirely to God is holiness and is the highest form of worship.

“And so Jesus also suffered outside the city gate to make the people holy through his own blood.  Let us, then, go to him outside the camp, bearing the disgrace he bore.” Hebrews 13:12-13 (NIV)

From, “Springs In Dry Places”, by H. Lamar Smith