I visited this country in late 2018.
While in Tanzania I visited the UNESCO World Heritage Site known as the Kilwa Ruins (with Silversea). This site was very impressive, and there were no other tourists around. We looked at the Malindi Mosque and cemetery, and Fort Gereza. These are all abandoned ruins that reflected the busy coast of East Africa centuries ago when the region was important for trading.
Of course, while at the historical site, there is always wildlife to be seen! Even in the heat of the day, I photographed sunbirds, bee-eaters, Mosque Swallow, and other birds.