Longfellow's Cabin

Longfellow's cabin is a a settlement that can be obtained by finishing the Walk in the Park quest.

While in build mode, the player will notice the buildable area is huge. You can in fact build on the entire island, not just around the cabin. You can squeeze a few water purifiers around the edges of the island, just before the green border.

Note also that you can create supply lines between the Longfellow's cabin and your old settlements in the Commonwealth, which is a nice detail.

Appearances
Longfellow's cabin appears only in the Fallout 4 add-on Far Harbor.