The only town of any size, Philipsburg is situated on a sand bar that separates Great Salt Pond, an etang or salt marsh, from the ocean. The entire town consists of two streets, Voorstraat (Front Street) and Achterstraat (Back Street), running the length of the isthmus and joined by short, narrow alleys. Many buildings date back to the early colonial era and, despite the multitude of duty free shops, Philipsburg retains a predominantly colonial atmosphere. The nine, shingled churches and the Queen Wilhelmina Golden Jubilee Monument are worth seeing. Nearby is Fort Amsterdam, dating from the time of the earliest settlers. Inland are the picturesque ruins of several plantation mansions, set in the wooded hills around Mount Flagstaff, and the Border Monument, celebrating 300 years of co-operation between the French and the Dutch.