as most users here said, it is under this path:
/usr/share/nginx/html
This is the default path, but you can make yours though.
all you need is to create one in the web server root tree and give it some permissions "not 0777" and only for one user and visible to that user only, but the end of the path is visible to everyone since the end of the path is what your files and folders will be viewed by public.
for example, you can make one like this:
home_web/site1/public_html/www/
whenever you make a virtual host in Nginx you can customize your own root path, just add something like this in your server block:
server {
listen 80;
server_name yoursite.com;
root /home_web/site1/public_html/www/;
}