Timbuktu is a real, historic city located in the West African country of Mali. It is famous for being a center of Islamic scholarship during the 14th–16th centuries and for its ancient manuscripts, universities, and trade significance on the trans-Saharan caravan routes.
The other options are incorrect:
- (A) It is not in China.
- (B) It is not fictional.
- (C) It is not a form of expression.
- (D) It is not in Mongolia.
\fbox{\parbox{0.97\linewidth}{
\centering Timbuktu is correctly identified as $\boxed{\text{a city in Mali}}$.
}}