Some of you may be thinking, hasn't this already been posted!?!?! Well, yes it has, but in the past people have just posted how to get the bridge, fountain and lighthouse/windmill and not posted any other information whatsoever so I'm going to post a complete guide on it.
The Bridge: Donate 200k to the town fund and the next day Pelly will ask you to vote for where you want your bridge, she will bring up a map with circles highlighting the places where you can put the bridge and you select which ever one you want.
The Fountain: After your bridge has been built donate 500k to the town fund, the next day Pelly will tell you that a fountain is being built. You do not get to choose where you want your fountain, it just gets put below your bus stop. Make sure there's nothing in the way of the fountain being built otherwise it will get erased.
The Lighthouse/Windmill: After your fountain has been built donate another 1 mil to your town fund, the next day Pelly will ask you to vote for either a Lighthouse or Windmill, again, you do not get to choose where you want it, it just gets put on your beach and next to your river. For every 1 mil you donate after the Lighthouse or Windmill has been built Pelly will give you a choice to change to the one you don't have. I'm not entirely sure if this happens for every 1 mil you donate, but I believe I have it right. Like the fountain, make sure there's nothing in the place it's going to be built otherwise it will get erased.
The Feathers: The feathers do nothing but they're a good way to show off how rich you are, it's just a shame that most people have transferred them over from their Wild World games. Donate 100 mil for the green feather, 200 mil for the blue feather, 300 mil for the yellow feather, 400 mil for the red feather, 500 mil for the purple feather, 600 mil for the white feather and 700 mil for the rainbow feather.
I believe each upgrade takes 1 week to be built, if I have this or anything else in this guide wrong, please let me know.
EDIT: Just something I forgot to include, apparently the Lighthouse gives an increased chance to catch rare fish and the Windmill gives an increased chance to get hybrids. I'm not entirely sure whether this is true or not but I have recently got the Windmill and I have been getting a lot more hybrids, I have heard similar things from people who have got the Lighthouse.
The Bridge: Donate 200k to the town fund and the next day Pelly will ask you to vote for where you want your bridge, she will bring up a map with circles highlighting the places where you can put the bridge and you select which ever one you want.
The Fountain: After your bridge has been built donate 500k to the town fund, the next day Pelly will tell you that a fountain is being built. You do not get to choose where you want your fountain, it just gets put below your bus stop. Make sure there's nothing in the way of the fountain being built otherwise it will get erased.
The Lighthouse/Windmill: After your fountain has been built donate another 1 mil to your town fund, the next day Pelly will ask you to vote for either a Lighthouse or Windmill, again, you do not get to choose where you want it, it just gets put on your beach and next to your river. For every 1 mil you donate after the Lighthouse or Windmill has been built Pelly will give you a choice to change to the one you don't have. I'm not entirely sure if this happens for every 1 mil you donate, but I believe I have it right. Like the fountain, make sure there's nothing in the place it's going to be built otherwise it will get erased.
The Feathers: The feathers do nothing but they're a good way to show off how rich you are, it's just a shame that most people have transferred them over from their Wild World games. Donate 100 mil for the green feather, 200 mil for the blue feather, 300 mil for the yellow feather, 400 mil for the red feather, 500 mil for the purple feather, 600 mil for the white feather and 700 mil for the rainbow feather.
I believe each upgrade takes 1 week to be built, if I have this or anything else in this guide wrong, please let me know.
EDIT: Just something I forgot to include, apparently the Lighthouse gives an increased chance to catch rare fish and the Windmill gives an increased chance to get hybrids. I'm not entirely sure whether this is true or not but I have recently got the Windmill and I have been getting a lot more hybrids, I have heard similar things from people who have got the Lighthouse.