Dark Land

Dark Land (more commonly known as Castle of Koopa) is the eighth and final world in Super Mario Bros. 3, but it is possible for the player to obtain two Warp Whistles World 1 and use them to reach Dark Land without having to play through the other levels. Dark Land is a sinister land where volcanic clouds cover the skies and block out the sun's light. One of the areas in the map is so dark that it appears to be completely black, except for a circle of light around Mario or Luigi.

Dark Land is Bowser's Kingdom, and is the place where his main castle stands. It is also the Koopa Troop's main base of operations, and because of this, the area is heavily defended by the Koopa King's military forces. Large numbers of tanks and airships patrol these lands, intercepting anyone brave enough to invade the Kingdom. Interestingly, Dark Land has a reference to the dragon's volcano in most systems.

Big Tanks
The large tanks are similar to airships, only on they are on the ground. Here, the player will meet up with Rocky Wrenches, cannons, and Rocket Engines. There is also one power-up in this level. At the end of the level awaits a blue Boomerang Bro.

Battleships
These battleships are similar to tanks, only in the water. As these are in ordinary water, Mario (or Luigi) will not be hurt if he jumps in. After avoiding obstacles and enemies, Boom Boom awaits at the end of the level. One can actually swim under the ship for the entire length of the level and emerge unscathed.

Hand Traps

 * 1) This contains every Hammer Bro. variety found in the game. The level starts with a Fire Bro. After it, there are two Hammer Bros. ready to attack. Also, there is a power-up in one of the blocks. A Boomerang Bro. awaits further into the level. The final enemy, a Sledge Bro. is encountered towards the end of the level. Once past there, the player can go up the pipe to claim a Super Leaf.
 * 2) The player must jump over Podoboos and leap onto platforms to reach the end. A Super Leaf is at the end of this level.
 * 3) The player must avoid jumping Cheep Cheeps in this level. At the end there is a Super Leaf.

Airships
A ton of tiny, Rocket Engine-equipped jets patrol the night sky. Rocky Wrenches are found on most of the jets. At the end, Boom Boom awaits to battle. After the player attacks Boom Boom twice, it'll start to fly.

'''8-1
At the start of the level, there is a Switch Block in the air, which reveals many blue coins closer to the ground. The player can use a Super Leaf or Tanooki Suit to fly from the very first platform to a pipe way up high where three 1-Ups are. Further into the level, a ? Block near a Venus Fire Trap's pipe withholds a power-up. A row of bricks is soon found. In between the tall multi-Bill Blasters, within a ? Block, there is a Starman. A hidden 1-Up Mushroom can be found within a long line of blocks. Then, the player must use a red Koopa Paratroopa to leap over a very tall Bill Blaster. The player can jump out between the two Blasters. The ♩ Block nearby will send the player across the gap. After this, the player needs to leap over the Piranha Plant and the level will be completed.

8-2
At the beginning, the player can either fall through the quicksand or enter one of the pipes, or jump over the quicksand. In the latter case, this level is the second and final to feature the Angry Sun, which is very rare. The player must avoid multiple Venus Fire Traps; eventually, a block containing a P-Switch can be found. After the ♩ blocks hovering over a pit, the player must ascend and descend the Venus Fire Trap populated hill. After the hill comes a small pit with one ♩ Block. The player must leap off a Koopa Paratroopa and bounce on the Note Block to reach the exit.

Fortress
The level starts out with an area with blocks and a door. Further on, the player must maneuver on conveyor belts; however, there is lava below. To the left is a power-up, needed to complete the level. The player must repeat this process until he has secured a Super Leaf, which is to break the bricks to the right. To the right, the player must avoid the Thwomp and smash a way through the blocks. Next, the player must enter the third door to the right, entering the next room; here, the player must avoid the Thwomps moving diagonally. Then the player must enter another door. Then, the player has to keep right, entering the door placed on the metal blocks. The player must then press the P-Switch and run right, entering the door at the end without stopping. After coming out of the door, the player has to keep moving, until two coins, unmoving, wedged between the metal blocks and a conveyor belt, are spotted. The player must wait until the P-Switch wears off, sneak under them, and hit the right one for a P-Switch again. The player can then enter the door that appears to the farthest right. Then, the player must wait again for the P-Switch to wear off, and duck as the belt carries the player safely under the spike battle Boom Boom.

Super Tanks
The player must avoid Bob-ombs, Rocky Wrenches, and other hazards on these huge tanks. At the end, Boom Boom will battle the player for the final time.

Bowser's Castle
In the final level of the game, Bowser has set up several traps. Near the start, statues with laser vision attack in place; if the player jumps over them, he or she can reach brief safety. Then, ride the platform up, taking the Donut Lift down. Here, ascend the staircase, avoiding the Roto-Discs. At the top the player must go back down to the ground on the other side. Alternatively, there is an extra life at the top right of this section, in a hidden block. If the player ducks and jumps on top of this block, they will float through the wall, skipping the descent. Afterwards, a lake of lava with Donut Lifts and Podoboos looms. In an alternate route, the player can go up and head right. If the player keeps heading right, avoiding the pool of lava and dodging fireballs, a door awaits. Once again, there is a room with statues and fireballs. Then, the player must go through the door at the far left. This is where the battle with King Koopa takes place.

King Koopa can be defeated with either fireballs or hammers. In battle, the Koopa King will leap up occasionally, crashing down into the weak floor, making an indent. King Koopa's only other attack is his ability to breathe fire. If King Koopa breaks through the whole floor, he's defeated. The door to the right will open and flash. Enter to find a distraught Princess Toadstool. She'll thank the player, then scamper off. The game ends and the credits scroll.

Trivia

 * Dark Land's music bears some possibly intentional resemblance to the Mars movement of The Planets, fitting as this movement is subtitled "The Bringer of War" after Mars, the Roman god of war.
 * In the GBA version, this area was known as Bowser's Castle in the International versions.