Christiansborg Palace, Copenhagen (must see)

The seat of Danish government today, housing all its three wings – Parliament, Supreme Court, and Prime Minister's office, this site is considered the birthplace of Copenhagen, as it comprises the ruins of the city's original 12th-century fortress (now literally under visitors' feet). Dating from 1928, the current palace is the sixth building to stand on the spot in 800 years, after a series of fires and reconstructions. Despite its relative recency, the majesty here is excellent, with all of the furniture, tapestries and exhibits in excellent condition. Paper slippers are put on to protect the beautiful parquet floors.

If you have the Copenhagen Card for tourists, admission to the royal reception rooms (as well as the nearby stables, kitchen, and underground ruins) is free. Highlights of the experience include the Queen's china collection; her ornate ceremonial library; and the Great Hall, which today is adorned with tapestries chronicling Denmark's history. The detail in the hand paintings that cover every square inch of some of the rooms is simply amazing.

If you don't have the Copenhagen Card (or don't want to pay to get in), it is still possible to walk around the courtyard and go up the tower (Copenhagen's tallest), where a nice observation area looks over the city on all sides. There's even a small elevator that takes groups of 8ish at a time to the top, so definitely do this, if nothing else.

Why You Should Visit:
The library is the stuff of dreams, and one could easily spend an hour looking at the modern tapestries.

Tip:
Always look out for the free English hour-long tours included in your ticket (they are at 3pm each day but also at different times in the weekends: 12pm/2pm), unless you'd rather wander the rooms on your own, reading the descriptions.