wuts a good metaphor for a cell and any place (preferably vacation)?

[lynn1]

example: a school. the metaphor is the fences surrounding the school is like a membrane in a cell
the cell structures are nucleus, nuclear envelope, ribosome, golgi, dna, cytoplasm, mitochondria, and cell membrane

you dont have to list all that; just give me some good places please :]!

thanks Dx!!