Chesapeake Bay Bridge Tunnel

An innovative variant on the famed Golden Gate Bridge. It is a sexual act involving 2 girls and 2 guys. The 1st guy on the far side of the bed is doing one of the girls doggy style (The start of the Bridge/tunnel). The girl he's doing is performing cunnilingus on the other girl (the tunnel, 'cuz she's down under) The girl receiving head is performing fellatio on the other guys, on the other side of the bed, completing the bridge tunnel.