Task: Text Categorization
Input (English): Context: The Mira River is a Portuguese river located in southwestern Alentejo.Its meander length is 145 km.It has its sources on the northern slopes of the Serra do Caldeirão and pursues a southeast-northwest course with a generally mild inclination to the Atlantic Ocean where it discharges through a small calm delta near the town of Vila Nova de Milfontes 115 km south to Lisbon.
Question: The document can be classified to which topic? 
Options: 1)Plant, 2)OfficeHolder, 3)Athlete, 4)NaturalPlace
Output (English): 4