Splash Hill Zone is the first Zone of Sonic the Hedgehog 4: Episode I. The level was featured in the official trailer on Sega's website and was the only playable level in the E3 2010 demo.
Splash Hill Zone is a tropical coastal area with rolling hills and a view of the ocean similar to Green Hill Zone and Emerald Hill Zone, and contains many of the same concepts, such as spinning sunflowers, Moto Bug Badniks and oddly-shaped palm trees. Later Acts in the Zone feature additional gimmicks, with the second Act featuring swinging vines for Sonic to grab on to, and the third Act having zipwires to ride across gaps.
The different Acts in this level are set at different times of the day; a similar system to Chaotix. The first two Acts are set during the day, while the third Act and boss Act are set at sunset, reminiscent of Sunset Hill from Sonic Advance 3.
- Act 1 - The Adventure Begins
- Act 2 - High Speed Athletics
- Act 3 - Sunset Dash
- Boss - Showdown with Dr. Eggman
Episode Metal Act 4 - In Pursuit of Sonic...
The first Act of Splash Hill Zone is later visited by Metal Sonic as the fourth and final Act of Sonic the Hedgehog 4: Episode Metal. As with all levels in Episode Metal, Splash Hill is rearranged with slightly more difficult object and Badnik layouts, with the most notable being the removal of the bridge at the beginning of the Act.
After clearing the Act, Metal Sonic finds that Sonic and Tails have set off to a new adventure in the Tornado, and gives chase after the two using the rocket that Sonic used to get to E.G.G. Station Zone, which he had found sitting not too far from an opened Capsule.
||A beautiful coastal area filled with rolling hills and an everlasting feeling of summer, Splash Hill Zone is the embodiment of an adventurous paradise. As Sonic races through the smooth slopes and crisp rivers, he will also witness a spectacular sunset view from the top of the hills.
— Description on the Sonic the Hedgehog 4 website
||Bubbles — A blue bubble Badnik used for Homing Attack chains.
||Buzzer — Wasp Badnik, flies along and stops to fire a missile at the player, then continues flying.
||Chopper — A piranha bot that jumps from under bridges.
||Moto Bug — The classic insect bot that rides around.
||Newtron — Materialises in sheltered areas to shoot a projectile. Can also turn into a missile.