Only about a dozen of Maine's more than 60 lighthouses are located on the mainland. The rest sit on islands, reefs, ledges or breakwaters, and four are caisson-style stations with foundations completely submerged in the sea. To construct the latter, builders sunk an empty cast-iron cylinder in the water and filled it with concrete. They then constructed a lighthouse tower on this foundation, with a lantern on top and the keeper’s domestic quarters below. Many of the towers are white with a black cast-iron lantern on top, but colors also vary and architectural styles show characteristic Maine quirkiness.