Faanui Bay was the site of the US military base during WWII. At the southwestern end of the bay, a steep and often muddy track climbs up to an old WWII radar station atop a ridge complete with two giant defence guns that were installed by the US troops. There are stupendous views of the lagoon and the motu. These vestiges are difficult to find (no sign), so it's not a bad idea to join an island tour.