Data and Map portals are a rather heterogeneous group. Some are what is generally known as metadata servers that collect and organise all links to data within a country or region. While it at first glance might seem strange to cover data and maps under a common heading. The reason for this is that it is common to use an existing map as a background for visualising spatial data e,g visualising existing urban structures on a background of a historical map. It is also common to extract the underlying information from an existing map and thus create new data from the map e.g. extract historical streams and rivers.
The obvious is national mapping organizations that supply base data. But many other organizations, especially in the environmental and planning sectors also expose their data in some data repositories. Finally, you will often find public national or regional data on data warehouses that typically are called something with “opendata” such as opendata.dk or opendata.gov.uk. You can see a list of recommended metadata and repository servers here
GeoData-info.dk https://www.geodata-info.dk The main portal to official danish data. This is often a good place to start looking for data. It is managed by Styrelsen for Dataforsyning og Infrastruktur. The site is a simple to use although it is not always up to date and since it, as such contains no data but just links to external data and the eternal data might change the site, therefore, be out of data.