W2/Harbour
From Inselkampf
The harbour is your link to the outside world. It allows you to create large/small war/merchant ships and colonization ships. A harbour requires a level 10 mainhouse.
At level 1 a harbour will allow you to build small war/merchant ships if you have level 1 sail (See laboratory for sail construction info). A level 5 harbour and level 1 sail will allow you to build large war/merchant ships. A level 10 harbour and level 1 sail will allow you to build a colonization ship.
Further upgrades to the harbour have not been experienced yet, but all theorization predicts it only reduces ship building time(and not by much).