Tongatapu is the largest island in Tonga and home to about two-thirds of the country's population. It's flat — most of the island barely rises above sea level — and roughly triangular, about 34km from west to east. The north coast is a low reef platform; the south and east coasts meet steep limestone cliffs dropping into deep water.
Most visitors arrive here first, since Fua'amotu International Airport sits on the southern part of the island, about 21km from the capital. Nuku'alofa, on the north coast, is a low-key city of around 30,000 — a waterfront, a market, a palace behind a white fence, and not much that demands your time beyond a day or two.
The best reason to explore Tongatapu itself is the Ha'amonga 'a Maui Trilithon at the island's northeast tip — ancient limestone gateway stones from around 1200 AD, impressively large and set in quiet surroundings. The blowholes at Houma on the south coast are worth a detour when the swell is up; waves force through the reef with considerable force and noise. Kolovai Beach on the west end of the island is the place to swim, and the area's flying fox colony (one of the largest fruit bat populations in the Pacific) roosts in the casuarina trees there.
Tongatapu's drinking water comes from underground — rainwater percolates down and floats on top of the heavier saltwater below, forming a lens that's pumped for the town supply. Rainwater tanks supplement this at most homes.
