Explanation:

- Correct Answer: Shandur

- Shandur is known as the world's highest polo ground, situated in Pakistan. It is located in the northern region of the country between Chitral and Gilgit, at an approximate altitude of 3,700 meters (12,139 feet) above sea level. The Shandur Polo Festival is an annual event attracting numerous visitors.

- Kasur

- Kasur is a city in the Punjab province of Pakistan, known for its rich cultural heritage and historical significance but not for a polo ground.

- Attock

- Attock is another city in Punjab, located at the edge of the Pothohar Plateau. It is noted for its historical fort but not for any polo grounds.

- Okara

- Okara is a city in Punjab, Pakistan, known for its agriculture, particularly dairy and farming, rather than being associated with polo grounds.