Go for a stroll by the water and breathe some fresh air at Kupang Harbor. It's always relaxing watching the boats as they come and go.
You'll have no end of sightseeing choices when spending time in Kupang. Kupang Harbor is a great place to kick off here, but there are numerous other worthy places to experience. Pura Oebananta, East Nusa Tenggara Museum, and University of Nusa Cendana are not far from the place for ships to anchor and will round out your day nicely.