Complex sentence: Portland Head Light is a historic lighthouse in Cape Elizabeth, Maine that sits on a head of land at the entrance of the primary shipping channel into Portland Harbor, which is within Casco Bay in the Gulf of Maine.
Split into simpler sentences: Portland Head Light is a historic lighthouse in Cape Elizabeth, Maine. The light station sits on a head of land at the entrance of the primary shipping channel into Portland Harbor, which is within Casco Bay in the Gulf of Maine.