People tend to check in during these times:
The inside is interesting to visit, especially the ballroom, but the best is the park and the castle view from the park.
Careful when going down to the coast - the Swedish network is stronger than the Danish there, so you might incur roaming charges.
The best part of the tour is the one in the basements, but you totally need a light source. Flashlights are for sell at the beginning of the tour for a mere 20dkk.
Free audio tour in Danish and English if you can pick up the wifi or Bluetooth.
Read Hamlet before going.
goes without saying - this is a must see - the old castle on the waterside of town.
Bring a torchlight, if you're visiting for the casemates/cellars. You'll need it!
Best coffee at KulturVærftet just along the harbour
Come in Summer. It was too cold in April
The Copenhagen Card gets you in for free. Very cool to walk through the casements.
А теперь - дискотека...
Замок Гамлета, принца датского. Особенно впечатлили подземелья и бальный зал.