What is this plant, please?

Hi,
I live in Ibiza, and often on my Wednesday morning walks I catch a waft of this highly aromatic plant, which in my olfactory memory seems to typify the Mediterranean maquis sort of habitat. I thought it was of the verbena family, but I have been told it that since it has alternate leaves it is not Verbenaceae, and judging also from the dried flower remains it is probably Asteraceae. But which species?
Many thanks.







[/size]