by Fyllis Hockman For people contemplating an Africa safari, the first place that comes to mind may well be Kenya. But many aficionados favor Tanzania, thanks to its vast Serengeti plains and a nearby volcanic caldera called Ngorongoro. On my trip to this East African country not long ago, Ngorongoro was far and away the star. Occupying just 102 square miles (264 sq. km), this 2½-million-year-old…