Saint Basil's Cathedral shows that architectural composition can be built not from a single great interior volume but from a cluster of independent small units. While the Renaissance ideal of the central, symmetrical, single-domed church matured in the West, Moscow followed a quite different logic: multiplicity, vertical emphasis, and external silhouette.

The building is in fact not one church but nine separate chapels gathered on a common base. At the centre, instead of a dome, rises an internal octagonal tent-tower (shatyor); around it eight chapels of differing heights and forms, each crowned by its own onion dome, form a symmetrical yet animated cluster. The interiors are surprisingly small and labyrinthine — all the building's energy lies not inside but in the three-dimensional silhouette outside. This means the church was conceived not as a 'gathering volume' but as an urban object, a monument-sculpture.

The onion dome itself is functional too: its steep, pointed profile sheds rather than holds snow, and it is built lightly as metal sheathing over a timber frame. The colourful, twisted domes were added in later centuries — the original may have been plainer. Saint Basil's points to an original synthesis blending the Byzantine dome tradition with the verticality of Russian wooden churches and the tent-tower form; it is the best-known example of a design sensibility that privileges not the interior but the outline drawn against the sky.