The downtown skyline is the part of any GTA city that goes on the cover. Vice City's, in Trailer 2, is taller and denser than any GTA city before it. That's worth thinking about.
This is a focused piece on skyline specifically. For downtown geography, see the downtown piece.
What the skyline looks like
Multiple high-rise blocks of distinct architectural eras - mid-century, late-century, contemporary glass. A handful of buildings noticeably taller than the surrounding cluster, framed as the dominant towers. The skyline reads as a real Miami / Brickell line, not a stylised cartoon.
Density of high-rise count looks higher than GTA V's downtown Los Santos. There are more towers, packed closer together, than the LS skyline supported.
Why this implies a larger urban core
A bigger skyline means a bigger downtown. A bigger downtown means more streets and more interactable buildings. None of that is mathematically forced, but it's how Rockstar's environment design has worked across previous games. We can't read measurements off the skyline shot - what we can read is intent.
A specific implication: the area you can drive through downtown is probably larger than GTA V's downtown. Whether that scales to multiplied interior counts is a separate question covered in the density vs size piece.
What the skyline tells us about period
Contemporary, unmistakably. The towers are 2020s glass-and-steel architecture, not 1980s art deco. That's consistent with the period framing - GTA 6 is set in the present, not in 1986 like the original Vice City. The art deco lives on the beach strip; the modern stuff lives downtown.