Hotel Accommodations
Rotterdam has almost 50 hotels from five stars to budget and more then half are located in the center on walking distance from the conference venue. The easiest way to book your hotel is at: http://www.rotterdam.info/uk/hotels/.
The booking site: www.booking.com gives special reductions for the the Westin Hotel (5 stars and closest to the conference venue).
For hotels close to de Doelen, please check: http://www.hotels.co.uk/hotel-netherlands/hotel-rotterdam/de-doelen-hotel-rotterdam/