A longtime Las Vegas land investor has paid a hefty sum for a large tract south of the Strip.

And it’s the same plot where, as seen in public announcements, the group behind a never-built futuristic minicity in Las Vegas now wants to build a sports arena. But several months after it unveiled its latest multibillion-dollar idea, it still hasn’t filed any project plans.

Seven Valleys Realty & Construction owner Khusrow “K” Roohani and partners bought around 70 acres at the northwest corner of Las Vegas Boulevard and Blue Diamond Road for $140 million, according to property records and business-entity filings.

They bought the land through multiple transactions over the past year from Las Vegas developer Scott Goldstein, and the final sale closed last month.

At the very least, the sale marks another sharp rise in value for a big property about 3 miles from the south edge of Las Vegas’ famed casino corridor.

Plus, another supersized project has already been pitched for the still-vacant site.

Las Vegas has a…