From the Super Mario Wiki
The player starts outside of the pyramid, and entering the door halfway up the pyramid will bring the player inside. Here, the player will have to jump up some stairs with a Buzzy Beetle coming down and will find a ? Block containing a power-up at the top. Beyond the ? Block, the path splits into three, with the center and bottom path being blocked off by Brick Blocks. Kicking a Buzzy Beetle into the block or using a tail swipe if the player is powered-up with a Super Leaf will break a block and open the path. Taking the center path will lead further into the pyramid, and using the pipe with a Piranha Plant in it as a platform, the player can reach the upper-left path to continue further. Breaking the blocks ahead on the next right path will lead to an open area with an overhead Warp Pipe; finding a Hidden Block to get over the wall and through the pipe will lead the player to a secret area with Brick Blocks and a Switch Block that will turn them into coins. After the initial entrance pipe is a long slope that will end at a pit and the exit pipe from the secret area. Continuing on, the player will find grounded Buzzy Beetles and ones hanging from the ceiling that the player has to use to break open the Brick Block wall to continue. After going through the Warp Pipe, the player will reach the goal alongside a Boomerang Brother. In the GBA version, a Blue Coin-revealing Switch Block on the redesigned other side of the pyramid has been added behind the pipe.