Grand Metropolis Act 2 shifts to a more urban, futuristic environment. This stage introduces more complex platforming and enemies that require specific character types to defeat efficiently. Start by using Sonic to grind on the numerous rails. Pay attention to the rail switches; some lead to bonus areas or shortcuts. You'll encounter flying enemies that are best dealt with using Sonic's Homing Attack or Tails' Thunder Shoot.
There are several sections with large gaps that require Tails' flight to cross. Look for glowing blue platforms that can be lifted by Tails to reveal pathways or items. Knuckles will be needed to break through metal crates and destroy larger, armored robots. Keep an eye out for the occasional laser grid; these can be bypassed by finding a switch or using a well-timed jump. The stage culminates in a series of high-speed sections leading to the goal ring.