You can take the elevator down to the abandoned tower basement in Baldur's Gate 3, but the elevator requires players to use the Flower of Light to activate it. After it is activated, you can ride down to the basement.
First of all, players need to go west from the location of the Shark Lizard, and they will see a mysterious tower in the past.
Open all the boxes around the tower and you will see a unique magic shoe. Put it on and jump on the mushroom.
You can find something like a generator on the bottom floor, which needs to be started with the Flower of Light.
PS: The Flower of Light can be found at the bottom of the tower outside the door.
After starting, the elevator will also start. Note that the monsters that appear also need to be defeated by the player.