We were able to arrange a special rate at the NH De Ville Hotel in Groningen for you. The special rate can be booked here until end of February 2019, and is on availability.

Go to their website or contact them directly
Phone: +31 50 5848121

For single use the special rate is € 110.00 per room per night including breakfast. For double use it is € 126.00 a night. This does not include the municipal tourism tax  € 3.15 per person per night.