Emptying the moat
The little one and eldest one joined me on my last day off, we visited ‘Slot Loevenstein’, a 14th century fortress in the Dutch waterline defense system.
Best time was spent on the waterpump playtable. They have a rough understanding of how a pump moves water from one place to another, hence their try to get the water in the moat to lower. They didn’t realise the pumped water was also returned to the moat (and I wasn’t going to tell them ;-)