According to Google cache, the robots.txt file and sitemap, it used to be a WordPress-powered link directory that you could pay to submit a link to and purported to offer "authority" to boost your search engine rankings. At some point recently, they probably threw an "exit" or "die()" into the index file: all the pages are there but returning no content. The millions of links were likely created by the site's owner's own other sites/domains; a spammy link network to game search engines again. There's tons of link and content farms like this out there trying to manipulate Google search results.
They seems to be registered at "Directi Web Technology Pvt. Ltd" which is a domain register.
It also doesn't say it is the top sites in the world as in visited. It just says that these are the sites being linked to by other sites (in the root dir).
Feels to me that this company set up 1.6 million websites all having links to these URLs. Because they all have the same amount of websites linking to them.
