They have several days and times. You sign up at the reception desk. Both bridge and galley tours are available. I've done the full tour on Mariner, but, missed the PG tour.

VOYAGER:
MC to FLL 11/07
MC/Dover 6/06
MARINER:
BCN / Ven 10/11
Alaska 2001|2006
Panama Canal 2003
NAV
Caribbean 11/06
Bermuda|New Eng/Canada 6/04
PG 5/05
OCEANIA
Nautica |Ist/Athens 6/07
Regatta|Baltics 6/08
Riviera 2013 Crossing -Istanbul to Miami