Promotional value expires 90 days after purchase. Amount paid never expires. Limit 3 per person, may buy 2 additional as gifts. Valid only for option purchased. Must sign waiver. Call ahead for available times. Admission is subject to availability. Not valid for special events or exhibits. This promotional pass is redeemable for general admission passes for a Crystal City Underground Barge Ride or walking tour.. Merchant is solely responsible to purchasers for the care and quality of the advertised goods and services.