From a rating for 1 to 10, I would rate it to 8, because it was very tiring and it was such a long way away to cycle. I think cycling slowly is better, because you can catch your breath, and you can observe many things more. I think cycling is fun, because it's a great exercise and it's eco-friendly!
I agree with the last comment - cycling is great exercise and eco-friendly as well as a lot of fun. Cycling slowly is fun because you get to see a lot of things, cycling fast is good exercise and you can cover a longer distance. My absolute favourite is mountain biking in forests on little paths - I have to really concentrate and there is nothing but me and nature.