"So, we are fighting an unknown homicidal force that has taken the form of your commanding officer and a cowardly alien, underwater, in a nuclear reactor. Anything else I should know?"
—The Twelfth Doctor

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

On the continent of Tazeem, rushing waters plunge through narrow canyons into mist-cloaked lakes.

Outlaws of Thunder Junction Commander

({T}: Add {U} or {B}.)
Sunken Hollow enters the battlefield tapped unless you control two or more basic lands.

Stranded far from home, the *FMS Northern Star* is a rusting hulk crewed by ghouls.

Fallout

Sunken Hollow enters the battlefield tapped unless you control two or more basic lands.

Even though these lands have basic land types, they are not basic lands because "basic" doesn't appear on their type line. Notably, controlling two or more of them won't allow others to enter the battlefield untapped.

However, because these cards have basic land types, effects that specify a basic land type without also specifying that the land be basic can affect them. For example, a spell or ability that reads "Destroy target Forest" can target Canopy Vista, while one that reads "Destroy target basic Forest" cannot.

If one of these lands enters the battlefield at the same time as any number of basic lands, those other lands are not counted when determining if this land enters the battlefield tapped or untapped.