This is an image of Neptune's Great Dark Spot of 1989.
Click on image for full size
NASA
Neptune's Great Dark Spot of 1989
Unlike Jupiter's Great Red Spot, the Great Dark Spot of Neptune is thought to be a hole, similar to the hole in the ozone layer on Earth, in the methane cloud deck of Neptune. The white clouds shown in the picture are above the "hole". In many images of Neptune, the Great Dark Spot can be seen to change size and shape.
The Great Red Spot of Jupiter is thought to be a hurricane which has been raging on Jupiter for at least 400 years. The Great Dark Spot, seen here by Voyager in 1989, disappeared (either dissipating or being masked) in 1994, and was replaced very soon by a similar "Spot" in a similar place, but in the north instead of in the south.
You might also be interested in:

This image shows the new Great Dark Spot of Neptune, which was discovered using the Hubble Space Telescope. The image shown here, shows a "hole" in the clouds of Neptune in pink, in the northern hemisphere,
...more
Like Jupiter and all the giant planets, Neptune's appearance shows a striped pattern of clouds. Other cloud shapes seen over time include a small dark spot, the "scooter" and the Great Dark Spot. The Great
...more
Neptune's atmosphere shows a striped pattern of clouds. This cloud pattern is very similar to that of Jupiter and Saturn. Neptune even has a Great Dark Spot similar to Jupiter's Great Red Spot. The history
...more
The giant planets have definitely changed since their formation. But how much remains to be seen. Most of the original air of the giant planets remains in place. (The earth-like planets lost most of their
...more
This image shows some clouds known as "cirrus" clouds, extending for many kilometers across the face of Neptune. These clouds are very high up, for they can be seen to cast shadows on the lower clouds,
...more
This image of Neptune uses false colors to show where the smog is. The smog of Neptune can be seen in red along the edge of the image. These hazes of smog are found at very high altitudes, over the clouds
...more
Scientists think that the solar system formed out of a spinning cloud of hydrogen and helium gas. Because the cloud was spinning, it flattened into a frisbee shape, just like a ball of pizza dough becomes
...more
If you had a quiz question in school that asked what year Neptune was discovered, you'd probably choose 1846. But Neptune wasn't discovered the way all the other planets in our solar system were. Astronomers
...more