I love walking
Living and working in London with all its public transport I hardly used to walk anywhere, then a few of us signed up for a 100k walk along the south downs way, enjoyed it so much we did that, or its sister event in yorkshire for 7 years in a row. Everything about it was fun. Planning your route, organising your supplies, getting up early to get out of the city and into the countryside, walking and talking with good friends, seeing unexpected things, country pubs, camping. Some of my best times over the last 10 years have been just simply out walking up and down hills looking around and getting lost with people, and the best thing about it is that its pretty much free. Split petrol between a few of you, pack some food and water, and head off, arrive home 14 hours later having well and truly worn yourself out.
Kids are finally getting to the age that they can cover a bit of distance now too and thankfully so far they enjoy it