The Cheonggyecheon reclamation was a major urban greening project that transformed the landscape of:

The Cheonggyecheon was not the only green space in Seoul that was converted to accommodate urban development during the mid-1900s. In the wake of the decades-long Japanese occupation and the ravages of the Korean War, 1960s South Korea refocused its energy on the future and successfully ushered in an era of economic growth

Explanation:

the enslaved people onboard suffered from illness with some frequency