The Clue Sea ___: place to build a castle
The Answer SHORE
The answer "shore" fits the clue "Sea ___: place to build a castle" because a shore is the land along the edge of the sea. This is often where people build castles, especially in coastal areas. Many famous castles are found right by the water, making the shore a perfect location. The word "shore" completes the phrase and makes sense in the context of building a castle by the sea.