The union of infinitely many closed sets is not necessarily closed. However, the Koch snowflake is compact: it’s the range of a continuous function defined on the compact set $[0,1]$, and continuous functions preserve compactness.
The union of infinitely many closed sets is not necessarily closed. However, the Koch snowflake is compact: it’s the range of a continuous function defined on the compact set $[0,1]$, and continuous functions preserve compactness.