The “Sweet Sixteen” cabins on Celebrity’s Millennium-class ships are a little-known anomaly: 8 cabins on each side of Deck 6 offer double-deep balconies for the same price as their otherwise-identical neighbors. For some reason, the Sweet Sixteen don’t appear on the deck plans (which depict the cabins as having shallow balconies just like the others on that deck). In researching our trans-Pacific cruise, I came across mention of these cabins and, since we booked very early, I found that nearly all of them were still available. (My booking agent had never heard of these cabins, but secured my preferred cabin.)