[prawn]

25km isn't too rough unless you're copping a lot of ups and downs, or don't enjoy walking. Helps if you start early to cover ground and give yourself time to rest.

Our 4yo daughter did day hikes in the 15-20km range a few times last year, in mountainous terrain. I think attitude and resilience are key.

In this case, one advantage was the author having a 7kg pack and using accommodation/food along the way rather than carrying a tent, sleeping gear, food, 2-3L of water, etc. Starting with day hikes or walking part of your commute is an easy way to build up to trying longer adventures.

[uwagar]

4yo hikes 15-20kms? man, sources please.

[prawn]

She was 4.5yo if you want to be picky. Some of the hikes were:

https://www.alltrails.com/trail/us/montana/grinnell-glacier-... (from where we started, this was 19km return plus climbing around at the top; I carried her on my shoulders for less than 1km)

https://www.alltrails.com/trail/us/idaho/sawtooth-lake-via-i... (15+ km and rained for part of it)

https://www.alltrails.com/trail/us/utah/chesler-park?u=m (16km)

In 2021 when my other two children were 6yo and 9yo, they did 40+ km in 24 hours. Hiked midday until 10pm and then 7am until midday the day after. They are just normal kids; I am not fit but enjoy hiking.

Here's that story: https://sarogaining.com.au/news/almertas-bluff/ https://www.instagram.com/p/CUUTaCcJfN8/?igshid=MTc4MmM1YmI2...

[LorenPechtel]

I've not personally seen a 4yo in the backcountry but a 6yo has climbed our local highest peak. 30km round trip with 1.5km of climb.

And how about this family:

https://thetrek.co/pacific-crest-trail/big-trail-big-family/

Their 4yo is to date the only 4yo to complete the AT. Now they have done the CDT at 6yo. These are both >3000km treks.