You can see it from the telescope on top of the lighthouse : it is on a seal island just offshore. (to the far right) To get the map, you will need to race Nate on the jet skis.
(Move the seals to one side of the seesaw rock to get the map out.)
(see related question)
Big Nate Island on the Poptropica map is the 9th from the top.
Go to your blimp and travel across the map to Big Nate Island.
follow it
where the chatty girls are.
Tilt the rock by moving the seals to the left side. You can now retrieve the paper, which is a map to the Time Capsule on Big Nate island.
if you don't get the keys you can't beat nate to get the map for the school.
Look through the telescope on top of the lighthouse to see where you are going : the seal rock has a map under it. Race Nate to the island to get the map.
you have to look all the way to the right
it's in the very left of the map
go to puffin point and go on the speed boat and race big nate. when you win go on top of the rock where the 2 seals are and push them to the left side then click on the map and you will have the map:)
You go to the harbour and click on the jet skies. after that you will compete with Nate to the island with the map.
talk to nate then find the the sixteen pieces of the map. (It only looks like less but find sixteen.)