Both my kids were born in Luxembourg. Our life, as for most people, radically changed after having kids. We became quite aware of the spaces in our city dedicated to kids. Our favourite park was in the centre. Google maps for some reason does not seem to see this as a park. But it is. And it is amazing for the kiddos.
The park is more geared towards older kids, but my then two-year-old enjoyed it also every time we went. When you go with younger kids, be prepared to so some climbing and obstacle races yourself.
There is a big 'pirate ship', connected to that is a climbing area with a long slide. Around it all is water play area which only is operational in the summer. There are swings for older kids and for babies.
You can't really see the water play area from these photos but it is pretty cool. Makes me want to be a child again :)
Here is my little one when he was around 2 years old.