Sitting atop Robert Koch Hill, the old German mansion is a Mwanza landmark with great views of the city and lake. Abandoned, it is a fun 'adventure'; several people now live here informally, but if you introduce yourself and give them a small donation (Tsh5000 should be OK), you should be able to look around. It is ill-advised to walk around the hill after dark.
Old German Mansion
Mwanza