Yes, Singapore Changi Airport (SIN) is one of the most interconnected airports in the world, and you can easily move between all four terminals in 2026. Terminals 1, 2, and 3 are physically connected and can be traversed on foot or via the automated Skytrain, which is free and runs every few minutes. These three terminals also surround Jewel, the massive glass-dome complex featuring the Rain Vortex, which is accessible via pedestrian bridges. Terminal 4 is a bit further away; to reach it, you must take a free 24-hour shuttle bus from Terminal 1 or Terminal 3. If you are a "transit" passenger (staying behind security), there are dedicated "airside" Skytrains and buses that allow you to move between terminals without clearing immigration. If you want to visit the public areas or Jewel, you will need to clear customs, visit your heart's content, and then re-clear security for your next flight. Changi is designed to be a "destination" itself, so moving between terminals is encouraged and very well-signposted.