Juneau is split between the downtown area and Douglas Island, connected by the Juneau-Douglas Bridge. The city is elongated along the waterfront, and many of the main sights are within walking distance of the cruise ship docks. However, to reach the Mendenhall Glacier, the airport, or Glacier Gardens, you will need transport.
By bus: Capital Transit runs a public bus network that covers downtown, the airport corridor, and the Mendenhall Valley. The glacier bus (Route 3 or 4, depending on season) runs from downtown to within a short walk of the Mendenhall Glacier Visitor Center. Fares are inexpensive. Schedules are available on the city's transit website.
By taxi or rideshare: Taxis are available in downtown Juneau; fares are reasonable for a city its size. There is no Uber or Lyft — local cab companies are the only option.
By rental car: Several national car rental companies operate at the airport. This is the most flexible option for reaching sights outside downtown, and driving distances within the road-accessible parts of the city and valley are short.
On foot: The downtown historic district, the waterfront, and the immediate hillside neighborhoods are all walkable. The Alaska State Capitol, the state museum, and the historic churches are all within 15 minutes' walk of each other.