I visited the Citadel as a solo traveller.
I went on a free guided tour which was very informative and interesting, they have demonstrations throughout the day of shooting the rifles and the canon which goes off at noon. I would advise people to visit in the morning to make the most of it.
They also have many exhibitions you can visit to warm up a bit of the weather is poor. The whole site is well maintained and all of the staff are in traditional costume which is really cool.