Juneau is mostly uphill from the docks. Put your good shoes on and go! You'll be able to pick up a city map either on your ship or dock. Juneau is the capital of Alaska, but you can't get there by road. Only by boat and/or by air.
One of my favorate walks is up hill to the House of Wickersham museum. If you don't feel like making the walk or are short of time, you can get a taxi. Judge Wickersham was a federal judge who came to Alaska to set up the judicial system. The mountains come almost down to the water. Juneau is built in a hard-to-find lower area. Go a few miles out of town in either direction and you promptly run into the end of the road as Juneau is surrounded by impassable 3,500 foot high mountains, huge ice fields and water. You might see folks panning for gold in the streams. Yes, gold can still be gotten that way. The saying goes in Juneau that you can still 'get a days' wages panning for gold'. Keep your eyes open. You might find a nugget and pay for your trip.
As you arrive in Juneau, you might notice some odd holes in the mountains facing the channel. These are the entrances to old gold mines. All of the commercial mines were shut down when World War II caused a serious shortage of labor in Juneau and Douglas, the village across the channel.
Have you noticed a few million trees by now?
The Alaska State Museum is great. It has exhibits on Alaska's natural history and colorful cultural history. There are exhibits on Tlingit, Haida and Aleut native cultures. I enjoyed seeing the kayaks made of seal skin which are the models for the modern ones we enjoy now.