Plas Menai Madness.
Hmm. Bangor is hardly known for its "Sports avtivitys". But by travelling a few miles or so out side of Bangor, you reach Plas Menai.
I recently went here to take part in rock climbing, canoeing, kayaking, sailing, hiking and various other outdoor and water sports.
It is situated right on the Menai Straights, meaning access straight into the sea.
Although hardgoing and sometimes very challenging, fun can be had and you come back to a nice warm meal!
I believe there is a swimming pool in side the building although I was outside so could not comment on this.
The instructors are very good, so I would reccomend this as in Bangor there is only a couple of gyms! And fresh air is lovely! All gear is provided.

Penrhyn Castle
Bangor High Street
Bangor Cathedral
The Smaller of the Twin Falls