Edinburgh castle has got to be the number one must see attraction within Edinburgh.  Due to the location of the castle, high on an extinct volcanic hill, it overlooks the entire city.  Almost anywhere in the city you can gaze up and see the castle.  It looks amazing in the morning fog and even more spectacular in the afternoon sun.\n\nThis is probably one of the largest castle compounds which I have toured as well.  The castle is quite well maintained and you can get stunning pictures both outside the city walls and within.\n\nOnce inside the castle there is a free guided tour which will walk you through the outside explaining all of the things to see in the castle.  I have been twice and enjoyed this part of the castle tour each time.  I recommend walking with this guided tour (it lasts about a half hour) and then independently exploring the different areas.  The crown jewels, the chapel, the dungeons, the war memorial and the WWI memorial with the top of the black volcanic mountain poking through the floor are probably my most favorite areas to explore.\n\nOn nice days and probably the weekends, the ticket line can be quite long however you can order online in advance or order from the hop on, hop off bus tours and walk straight through.  This saved us some time on our second trip to Edinburgh as our first trip, I spent about a half hour waiting.