I have recently returned from a cruise on board Queen Mary 2 that took in the port of Oslo.
Oslo is not an overlarge city and only has a population of around 590,000. The main berth and terminal for visiting cruise ships is very close to the centre of Oslo and the Oslo Hop On-Hop Off bus service stops at the cruise terminal.
Among some of the excellent sights we visited in our day there were the Nobel Peace Centre...
The Royal Palace...
The Opera House...
and Norway's most visited attraction, the Vigeland Sculpture Park...
A full review of my visit to Oslo can be found on my cruise blog...
https://solentrichardscruiseblog.wordpress.com/2013/10/18/one-way-to-do-oslo/As always I would be delighted to answer any questions. Answers are likely to have a much quicker response through the blog 'Comment' facility.