PDOK (Publieke Dienstverlening Op de Kaart) is the Dutch National SDI that provides many free maps and other geospatial services like WFS and an address-finder. PDOK has developed the public PDOKViewer with Heron to view all layers (WMS, WFS, TMS, WMTS, Atom) provided by PDOK. Click on the preview image below or go directly to the PDOKViewer at: pdokviewer.pdok.nl.
The Heron Map Context facility for layer definition and loading was developed by TNO in the context of the PDOK Viewer and later backported to Heron. More info on PDOK can be found at pdok.nl.