where does domain go in the 7 levels of classification
It is the highest taxonomic rank of organisms
Domain (biology)
In biological taxonomy, a domain ( or ) (Latin: "regio"), also superkingdom, realm, or empire, is the highest taxonomic rank of organisms in the three-domain system of 
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Domain (biology) [SEP] Introduction
In biological taxonomy, a domain ( or ) (Latin: "regio"), also superkingdom, realm, or empire, is the highest taxonomic rank of organisms in the three-domain system of taxonomy devised by Carl Woese et al. in 1990. According to this system, the tree of life consists of three domains: Archaea, Bacteria, and Eukarya. The first two are all prokaryotic microorganisms, or mostly single-celled organisms whose cells have no nucleus. All life that has a cell nucleus and eukaryotic membrane-bound organelles is included in Eukarya. Non-cellular life is not included in this system. Alternatives to the three-domain system include the earlier two-empire system (with the empires Prokaryota and Eukaryota), and the eocyte hypothesis (with two domains of Bacteria and Archaea, and Eukarya included within Archaea).