One of the most interesting cultural/geographical features I have seen in the Solomon Islands are the man-made reef islands that can bee seen in and around various lagoons.  Many of the original builders/settlers of these islands were displaced from the bush-lands many generations ago.  Slowly, canoe load by canoe load, these settlers brought pieces of dead coral and piled them upon one another, until their islands were built.  This picture is taken at mid-tide–the water level will rise a bit higher than seen here.  Historically, these sea people would catch fish and create shell-money (still an active currency) to be traded with bush-people for sweet potato, cassava, taro, etc.