Not only is Saffron City one of the biggest and busiest cities in Kanto, it is famous outside Kanto. The large Silph Co. HQ stands form as the cities center piece, while two gyms dominate the cities north-eastern corner district. Not only it is the business center of Kanto, it also holds the region's largest infrastructure, including the Magnet Train.
Ash goes to Saffron City in the Anime in order to get the Marsh Badge, but was unable to beat Sabrina's Kadabra with Pikachu. He continued his journey and later returned with a Haunter, however instead of battling Sabrina's Pokémon it chose to play around, causing the emotionless Psychic to burst into laughter. As a reward, Ash was presented with the Marsh Badge.
In Super Smash Bros.
There is a stage named Saffron City in Super Smash Bros. on the Nintendo 64 device. It consists of three skyscrapers with two hovering platforms. Flying Pokémon, such as Butterfree and Fearow, appear in the background.
When the player goes into Copycat's house and goes upstairs to her room and presses A on the TV with a SNES on it, the message log will say "A video game showing Mario wearing a bucket on his head." This is a reference to the video game Mario & Wario.
Saffron City is the largest city in the Kanto region.
Although Saffron City is the largest city in the Kanto region, it isn't the most populated city. Celadon City is more populated than Saffron City, despite it being smaller than Saffron City. This also happens in the Unova region.
It is the only city with two gyms, although one is a Fighting Dojo.