The city located at 90 degrees south latitude and 0 longitude is the South Pole.

Here's why:

* Latitude: 90 degrees south is the furthest point south on Earth, marking the South Pole.

* Longitude: 0 degrees longitude is the prime meridian, which runs through Greenwich, England and divides the Earth into the Eastern and Western Hemispheres.

Therefore, the intersection of these two lines defines the geographic location of the South Pole.