In eukaryotic cell transcription, RNA splicing and RNA capping take place inside the

In eukaryotes transcription takes place in the nucleus, where the DNA is located.
The primary transcript (hnRNA) contains both exons and introns and is non-functional.
It is processed in the nucleus: splicing removes the introns and joins the exons; capping adds methyl guanosine triphosphate to the 5′ end; tailing adds 200–300 adenylate residues to the 3′ end.
Only the fully processed mRNA is transported out of the nucleus into the cytoplasm for translation on ribosomes.
Hence transcription, splicing and capping take place inside the nucleus.