Final answer:
Peloponnesus is a large peninsula in southern Greece, connected to the mainland by the Isthmus of Corinth and separated by bodies of water, with Patra being a major city.
Step-by-step explanation:
The country with Peloponnesus, a large peninsula in the southern portion of the mainland, is Greece. It is connected to the mainland by the Isthmus of Corinth and separated by the Gulf of Corinth and the Saronic Gulf.
Patra, a significant city on the Peloponnesus, serves as a hub of commerce and culture for the region. This area is steeped in history, notably due to the Peloponnesian War, where Sparta and Athens were key opposing city-states in a struggle for dominance in ancient Greece.