Vattakottai Fort or ‘Circular Fort’ is a seaside fort. It was built in the 18th century as a coastal defense fortification and barracks in the erstwhile Travancore kingdom. It was constructed under the supervision of Captain Eustachius De Lannoy, an ex-Dutch naval officer of the Dutch East India Company, who became commander of the Travancore Army in the 18th century, after he earned the trust of the Travancore King Marthanda Varma. Eustachius De Lannoy constructed Vattakottai, as part of the defense fortifications he undertook throughout Travancore. Rectangular in shape and covers an area of about three and a half acres. The fort is enclosed by walls 25 to 26 feet high, including the parapet, 29 feet thick at the front, 18 feet at the corners and 6 feet at the rear. The fort is made of granite blocks and today is a part of the fort extends into the sea. It is a protected site under the Indian archaeological department. A major renovation of the fort was undertaken recently by the department, and the site is now a popular tourist spot. Vattakottai Fort commands a picturesque view of both the sea on the one side, and the hills (Western Ghats) on the other. Another interesting feature near the site is a beach of black sands.