What did Mungo Park explore?

He had to try to find the course of the River Niger in Africa as his first major journey and did others after that.

https://en.wikipedia.org/wiki/Mungo_Park_%28explorer%29#First_journey

Mungo Park was a Scottish explorer who led one of the first expeditions to investigate the course of the Niger river in Western Africa. Mungo Park was a 23 year-old scottish surgeon surgeon who had just returned from a journey to Sumatra on a ship of the East India Company. There he had discovered 6 species of fish, he had published descriptions in a Scientific Journal. In 1795, Park had gone to Piscina, on an offer to research further into Africa. Park had accepted and a severe fever overcame him during his journey. Park also had been captured by certain muslim leaders. After he had got out of the Prison he had wandered around and had finally found the Niger River. Park was amazed at how beautiful the River was. Park had stated "I saw with infinite pleasure, the object of my, mission". Park had returned home to London where became famous on his publications of his voyage across Africa.

Later in 1806 he sailed downstream to the Bussa rapids, where he drowned, trying to escape an attack by the Africans.
http://www.studyworld.com/famous_explorers_of_africa.htm

Mungo Park (1771–1806), a Scottish explorer. Leading two West African expeditions, 1795–97 and 1805–06,
Park became the first to explore the Niger River in modern times. On the second trip he traveled more than 1,000 miles (1,600 km) downstream, but was drowned in the rapids at Busa, Nigeria.

http://history.howstuffworks.com/african-history/mungo-park.htm

He attended the University of Edinburgh and was a surgeon. He wrote Travels in the Interior of Africa (1799) and the uncompleted Journal of a Mission to the Interior of Africa (1815).