Casinopolis is the casino level for this game, and it contains one of the chaos emeralds. To enter it, you need to hit the button above the sign in front of the building to unlock the front entrance. After entering the casino, you will need to play in one of two pinball games and obtain at least 400 rings.
When you enter a pinball table, you are given three balls. You can keep rings you collected, but will only be returned to the main hall if you have at least 100 rings.
Slots is a basic pinball table, with three star bumpers on the left, three ramps, and a loop.
The main feature of the map is the slot mechanic. To spin the slots, aim Sonic towards the middle ramp to start the reels. Press the action button to stop one reel; if you match three symbols on a horizontal or diagonal line, you will get a prize, winning a given number of rings.
A second feature of the table are two extra lives on the side. To unlock the ramp towards the extra lives, you need to hit a button between the ramps to lower the barrier. When it is down, launch sonic into the ramp
In this pinball table, there are three cards visible. If you hit one of them, it will be collected and a new one will be generated afterwards. Once you collect five cards, you will be rewarded with rings if you have matching carde. In addition, a match will open a door at the back of the table, where you can get cards more easily.
Of the options to collect the quota of 400 rings, this is the slowest, due to the extended scenes that may appear during transitions.
If you missed the quota of 100 rings in the pinball scene, you will be deposited in the sewer below the casino, filled with hazards.
There are multiple routes, but it is possible to collect enough rings to complete the stage here.
To complete the stage, you need to enter the ring vault, and deposit at least 400 rings. Rings are deposited by standing on the button, and will help create a surface that allows you to reach the chaos emerald at the top (in addition to removing an invisible barrier). Additional rings that are collected are used to build an optional decoration in the lobby.