Yes. (But you have already picked it up by now.)
In order to get the coin from the fountain in Poptropica Astro Knights Island, you must go to the fountain and look for the shiny coin. Once you spot it, you walk over to it and it will be added to your dock.
It is in the middle section under the rocket, and will show up as a shiny glint in the water.
Yes. You must Sit on the part of the fountain that has water on it. You will see something shiny. Click on it.
in main street you will find a fountain and walk where the shiny thing in the water is.
Push on the shelf in "Non-Fiction McM". This is written on the library slip found at the Mordred Museum, which you must first get. (Get the shiny gold coin from the fountain and pay your admission.)
The rolled up paper is on the shelf in "Non-Fiction McM". This is written on the library slip found at the Mordred Museum. (Get the shiny gold coin from the fountain and pay your admission.)
Before the shelf opens the secret passageway, you have to "know" it is there, by getting the library slip from the Mordred Museum. Get the shiny gold coin out of the fountain and pay your admission. The stack of books with the slip is in the front row.
Push on the shelf marked "Non-Fiction McM" on the lower aisle of the library. This is written on the library slip found at the Mordred Museum, which you need to open the passageway. Get the shiny gold coin from the fountain and pay your admission, and find the library slip in the stack of books.
It Is In town square (the shiny thing in the fountain) jump on it and boom, it's yours! :)
I assume that by dungeon you mean the dungeon on Astro-Knights Island. If not, then pay no attention to the rest of this. If you get the gold coin from the fountain, (walk over the shiny glare to receive it) you can pay for admission to the house of Mordred. Simply click "USE" when inside the house. Once the attendant lets you in, click on the large stack of books on the bottom floor. He (the attendant) will say that the books must remain the way they are but give you a library receipt. Now go into the castle (look on your map or go right until you see a semi-destroyed building). One of the two rooms on the bottom floor is the library. Look at the receipt. Underlined is "McM". If you go down the stairs, click on the McM button on the shelf. A secret trapdoor will open. Go down to get into the dungeon. If you need to get into the dungeon the SECOND time, purchase the Astro-Knights guide on Astro-Knights Main Street.
You take the sardines that you found in the tunnel and go up to the fountain you throw the sardines this will make the bird fly away then you go to the top of the fountain. There will be something shiny you click on it and it's Fiona's ring.
It's in the fountain next to the Mordred Museum. It is the shiny thing in the water about halfway up. Use it to pay your way into the Museum and find the Library Slip. (It is in a stack of books.)