On the border with the Democratic Republic of the Congo, a little over two hours east of Kigali, Kivu is one of Africa's "Great Lakes,"is about 56 miles long and 31 miles at its widest. Visitors can hike the lush landscape and go kayaking/canoeing/paddleboarding as well as take boat trips on the lake. In this same area, tour operators offer various eco, cultural, and adventure options.
Oh, and there's one other thing about Kivu: it's known to be one of the world's only three "exploding lakes," meaning every so often carbon dioxide and methane are explosively released from the bottom. But this hasn't occurred for a long, long time, and any danger to visitors is considered highly unlikely!