In the Netherlands, like in many other countries, it is not allowed to fly over closed housing-areas and/or groups of people. The red circle gives you a NFZ, and NO fly means NO fly. Fines are pretty heavy, and it will not only the plice, also other official enforcement officers (BOAs) are able and willing to act on people flying drones in restricted areas.
Be a good representative of the drone community, stick to the rules, it will benefit all.
Just checked for myself (I am in Groningen tomorrow), this link might help you:
In general, max. altitude is 120 meters, VLOS only, no night flights.
If you understand dutch, this link might be helpfull, if not, let me know if you need a translation.
Er zijn Europese regels voor drones. Deze regels gelden in alle landen van de Europese Unie (EU). En zorgen voor veiligheid in de lucht en op de grond.
www.rijksoverheid.nl