theres also an "underground city" in seattle
its the portion of downtown seattle that burned down in the fire of 1889. they kind of just built over it. i suspect thats what happend in san fran too.
i heard underground the seattle international district (china town) a lot of shit happens that you would never find out unless you were trusted and chinese. underage prostitution, general prostitution, drugs, gambling, etc. no im not a pervert, its well known that seattle has some of the worst human trafficking in the country.