Norfair, the fiery, volcanic hell of planet Zebes and can only be explored in full with the Varia suit as many of the rooms are super heated, exploring these rooms without the Varia results in your energy being drained quickly due to Samus not being able to cope with the intense heat. Norfair is the location that Ridley is usually fought in, in an even lower section of Zebes known as Lower Norfair.
In the original Metroid, Norfair is one of the game's main areas, and home to some of the toughest foes in the game. Norfair has some of the toughest enemies in the game and is abundant with pools of lethal magma, which hurt you even with the Varia Suit.
Unlike future titles, in the original Metroid the Varia Suit isn't explicitly required to explore Norfair, but the extra defense will be helpful!
 Super Metroid
Returning from the original game along with Brinstar and Tourain is Norfair. Like before Norfair is broken into two sections, upper Norfair and lower Norfair.
The major differences include music and number of heated rooms, and lower Norfair is full of Chozo based statues and technology, implying the Chozo used this place as some kind of religious temple. Ridley is also fought here.
Unlike the original Metroid, this time you'll need the Varia suit to fully explore Norfair as many super heated rooms exist, but you still need to explore some of the cooler sections of Norfair to obtain the high jump boots to get to Kraid's lair who is guarding the suit.
Gaining access to lower Norfair isn't that simple though as there is a room filled with lava that requires the Gravity Suit and Space Jump, with the Gravity Suit located in the Wrecked Ship and the Space Jump in Maridia.
 Metroid: Zero Mission
While Norfair is mapped similar to how it was mapped in the original Metroid, elements from Super Metroid also exist, including heated rooms. Norfair also features a lower Norfair, known as Ridley, which features Ridley as the area's Boss.
The Varia Suit is required to fully explore this region as a result of the heated rooms, a noticeable change from the original Metroid.