Which planet is famous for its Great Red Spot?

Jupiter. The spot is an anticyclonic storm wider than the Earth, and it has been continuously observed since 1830 - with plausible sightings back to the 1660s, which would make it at least 350 years old. Nothing on Earth lasts more than a couple of weeks.

It persists because Jupiter offers none of the things that kill a storm here. There is no land surface to create friction and no ocean to draw energy from and then exhaust; the storm sits wedged between two jet streams running in opposite directions, which keeps it spinning, and it absorbs smaller storms that drift into it.

It is shrinking, and fast enough to watch. In the late 1800s it was perhaps 40,000 kilometres across and could have swallowed three Earths; it is now around 14,000 and roughly circular where it used to be a long oval. Whether it is dying or entering some other stable state is unknown - which means the most famous feature of the largest planet may be a temporary thing that we happened to arrive in time to see.