A few hundred metres offshore at the southern end of Mwanza's main harbour stands the rock that defines the city — a single granite boulder weighing tens of tonnes, balanced apparently impossibly on top of a small stack of smaller rocks just above the lake's surface. The whole composition looks like it could topple at any moment but has stood, broadly unchanged, for at least the past century and a half. It is on every postcard of Mwanza and gives the city the nickname "Rock City."
The rock is easy to see from the lakeshore promenade in the centre of town — bring a long lens for a clean photograph. Closer access is by short hire-boat trip from the small jetty near the ferry terminal; the boats also pass the colourful fishing dhows moored in the harbour. Late afternoon, when the sun is low behind it, is the moment to be there.