Ketchikan is known as Alaska's First City, because she is the first one encountered heading north along the coast, but for the Princess itinerary we've been following, she comes as the last port in Alaska.
I'd have to call "city" a gross exaggeration. Ketchikan is quite small, and I wouldn't plan on spending a full day just browsing the town. That can be done easily in an hour or two max. Still, this is a quaint town in a gorgeous setting, and if you want to lounge away the day nursing an Alaskan Amber or hot cocoa, you can anchor into a table for the duration. If you've been extremely active in the other ports, that could be a nice change of pace.
In any case, you'll want to stroll along clapboard sidwalks through the quaint village at some point, perhaps combining that with a hike through the largest temperate rainforest in the world located just outside of Ketchikan or attending the The Great Alaskan Lumberjack Show.
Of course, you can explore on your own if you like, although you should keep an eye out for bears and slippery rocks if you hike through the rainforest on your own, as Julie and I did on a prior trip. While no bears came around to scare us, realizing that no taxi would be returning to pick us up and wondering if we could hike back to the ship before it sailed did put a good scare into us, so I would recommend going with a tour if you head out of downtown.
Princess offers an incredibly diverse menu of excursions for those ready to spend more freely. How about exploring Misty Fjords by Seaplane, spotfishing for salmon or ziplining through 17 1/2 million acre Tongass National Forest, the largest park in North America?
Better service leads to better trips!