Peter: Most of the Danish power outlets I've seen look like this:
But maybe older outlets don't have the ground contact.
Here in Germany these are the only power outlets you'll find in walls:
And these are the corresponding plugs:
Called Schuko (pronounced like "shoe co"), which is short for "Schutzkontakt", which means "protection contact". The plug is actually a slightly universal plug, as it fits German power outlets (which have the ground contacts on the top and the bottom) and e.g. French ones, which have a pin on the power outlet which fits into the hole on the plug.