New Zealand

New Zealand's backpacker culture is so well-established that the country essentially runs on solo travelers and working holiday visa holders. The "Great Walks" (Milford Track, Routeburn, Tongariro Alpine Crossing) are world-class multi-day hikes with maintained huts and booking systems designed for solo hikers. Kiwis are legendarily friendly — hitchhiking is still common and safe. The country is compact enough (similar size to the UK) to see both islands in 3-4 weeks. Hostels are everywhere and social by design. The Lord of the Rings tourism circuit alone could fill two weeks.