I've always wanted to add something nice to my garden. I finally came up with this. I did it in creative but it can be done in survival too. For this instructable you can just follow the pics. I hope you like it!
Step 1: Pillars
(You can use any type of planks). Make a five block tall pillar. Do three more, each for blocks away from each other (as shown above), and then connect (also shown).
Step 2: Dig N Fill
Dig a trench one block deep, lining up with the pillars, and remove the block below each pillar. Now fill with water. It doesn't have to be still, but I did that because I'm in creative mode. Add a block in the water for the bridge.
Step 3: Plow N Plant
Plow the island. Don't plow your bridge block.
Step 4: Fence
Put a fence and gate as shown above.
Step 5: Back to Structure
Add glass blocks as shown above. The last pic is what it should look like from the inside.