How far is it to walk from Edinburgh Castle to Palace of Holyrood? Also, I would like to see the Royal Brittanica, and can't seem to find on the internet whether or not you can walk there or if you need to take a bus (if so, which one)?

Well, they don't call it the Royal Mile for nothing! (think it's more like 1.25 miles)

You can walk out to Leith (I have) but it is quite a hike -- finding the bus routes will be easy once you get there.

Look here for bus lines. Long walk from Holyrood.

http://www.edinburgh-waterfront.com/map22.html

Walking the Royal Mile is easy since it is all down hill from the Castle to Holyrood. Since are plenty of places to visit along the way (ST Giles Cathedral, Gladstones Land, the Whisky Center, Camera Obscura, museums, shops, and pubs) it is good to allow at least a couple of hours for the walk.

You can take a public bus to Leith -- or you can buy a combined bus/ship's tour ticket at Waverly Bridge. The tour bus drops you right at the Yacht and you don't have to wait in line to get in.

Do a search for the Royal Yacht Brittania, its not Britannica. Perhaps that is why your search didn't turn up anything. I was there in December. It was great. Hope this helps.

How long does the tour of the Brittania take. Also how long do you need at Edinburg Castle and Palace of Holyrood?