Which wall is considered the second longest in the world after the Great Wall of China?

The Kumbhalgarh Fort, known for possessing the world's second-longest wall, after the Great Wall of China, is a UNESCO World Heritage site. It is nestled 84 kilometres north of Udaipur amidst the beauty of the wilderness.
https://www.incredibleindia.gov.in/en/rajasthan/udaipur/kumbhalgarh-fort#:~:text=The%20Kumbhalgarh%20Fort%2C%20known%20for,the%20beauty%20of%20the%20wilderness.

By comparison with the Great Wall of China (21,196 km), The Kumbhalgarh Fort mentioned in the previous answer is a mere 36 km in perimeter.

Hadrian's Wall in the north of Britain runs some 117 km.

The Walls of Benin in Nigeria measures 16,015 km, according to https://en.wikipedia.org/wiki/List_of_longest_buildings .

There is a wall in the world that is about 1700 miles long.

The Moroccan Western Sahara Wall (also called the Berm) is the second longest after China's Great Wall, at about 2,700 km (1,700 miles). Morocco built it from 1980 to 1987 to separate their controlled areas - with key resources like phosphates - from the Polisario-held Free Zone. The wall is heavily fortified with sand berms, bunkers, fences, radar and the world's longest continuous minefield.

https://en.wikipedia.org/wiki/Moroccan_Western_Sahara_Wall