Christiansborg Palace & Slotsholmen

This is where the city began. In 1167 Absalon built a castle of limestone and flint out here on the islet, not to live grandly but to keep pirates out of the sound. A village grew around it, the village became a harbour, and the harbour became a capital. The castle is gone. But go down into the cellars beneath the palace and you are standing inside it. The ruins of Absalon's curtain wall and foundations were excavated and opened to the public in 1924, and you can put your hand on masonry he had built. It is the oldest thing in Copenhagen you are allowed to touch. Above it, this plot has had trouble holding on to a building. The first Christiansborg burned in 1794 and left the royal family homeless. The second burned in 1884. The third, the one in front of you, went up between 1907 and 1928 and has been allowed to stand so far. And there is something about this house that exists nowhere else in the world. Parliament sits here and makes the laws. The Supreme Court sits here and rules on them. The royal family keeps its state rooms in the same building. Three branches of government, one address, one roof. In most countries somebody would have called that a bad idea. The tower is open to visitors, and the view from it is the best in the city.