Why is holland flat?

The Netherlands is not completely flat. There are some rolling hills in the southern and eastern parts of the country. Overall though, the Netherlands is flat because it was formed by sediment deposits from rivers and glaciers. The Rhine River and the Meuse River have carried sediment from the Alps and deposited it in the Netherlands over millions of years. Additionally, glaciers that covered the Netherlands during the last ice age left behind sediment when they melted. This sediment built up over time and created the flat landscape that we see today.