During the Carboniferous, some 299 to 359 million years ago, it was very hot and humid on earth. The Netherlands was situated around the equator at that time, so here too it was a very different climate than it is today.
Tropical swamp forests with many plants and large insects and amphibians emerged. There were even giant dragonflies with a wingspan of 70 centimeters! There were also a lot of ferns, which you can still encounter today. Find out what they look like on the internet and try to find one when you walk outside or in the garden.