Land activities on Tonga are limited to the small size of the islands' land mass. The main island of Tongatapu has some interesting archaeological sites as well as blowholes and natural stone arches along the south coast. There are two good tour companies based in Nuku'alofa offering half day sightseeing tours of the island, and some of the small resorts at Haatafu Beach arrange their own tours for guests. No tours are allowed to operate on Sunday.
Car hire is available in Nuku'alofa but you will need to get your driving license endorsed before driving - speed limits are a meagre 40km on most roads and strictly and regularly enforced and pigs running across the road and kids playing are major hazards. A more relaxing way to see the islands on your own is to hire a taxi which are pretty cheap and your driver is most likely to give you a good insight into the island and its culture.
In the outer islands, land activities are even more limited. There are no tour companies on Ha'apai or car hire, so the island is best explored by foot or bicycle. Vava'u is slightly better for organised land tours with sightseeing excursions into the hills and a couple of car rental companies and moped hire outlets in Neiafu Town for exploring the island yourself.
Hiking in Tonga
The best hikes on Tonga are on Eua Island (off Tongatapu) where there are excellent walking trails through light forest and along coastal cliffs. There's also a good coastal walk along the south coast of Tongatapu taking in the natural stone bridge and blowholes. On Vava'u, the best hike is a forty minute trail leading to the summit of Mt Talau, a flat topped volcanic peak overlooking Neiafu Town and the Port of Refuge with wonderful views.
Tonga has some of the most interesting historical sites in the South Pacific with royal tombs and an impressive stone trilithon on Tongatapu. The most impressive of these is Ha'amonga a' Maui which consists of three massive limestone slabs, one of them cut into and resting on top of the other two pillars standing over 5 metres high. On Tongatapu you can also see memorial stones marking the spot where Captain James Cook landed in 1777 and where the first missionaries landed on the opposite side of the island.
Shopping in Tonga
Tonga shopping is very limited with the best items on sale being traditional hand crafts, local coconut oils and fresh produce. Basic clothing and cosmetics can be purchased in Nuku'alofa and Neiafu towns but you wont find any decent electronic stores for cameras or shops selling or renting snorkelling, surfing or fishing equipment so you'll have to bring everything with you. The best place to find souvenirs a is either at the Women's Handcraft Centre or the Talamahu Market, both in downtown Nuku'alofa.