A Russian fort in Hawaii? Yes, really. Constructed in 1817 above the southern bank of the mouth of Waimea River on the site of an ancient heiau (temple), the octagonal Fort Elizabeth was named after the Empress of Russia. Only its impressive outer walls, some 20ft high, are still standing. It once harbored a Russian Orthodox chapel and a cannon.
Follow the trail 100 yards beyond the fort to reach a pretty riverfront beach. While not suitable for swimming, it makes for a pleasant afternoon stroll.