November's monthly patron poll map - a continuation along the path from the Palace Dungeons, down to the well underneath. You can see how we got here by checking out the palace map and the first level of dungeon.
This map is intended to fit with some of the general lore of Waterdeep and the Palace; but certainly with my own spin on it. Forgotten Realms wiki mentions the well beneath the palace, the water supply; I also wanted to give this a Living Waters of Mandalore vibe. Initially there were prison cells here, but those morphed into change rooms, and a bath house, and...
let's dive in (pun intended).
Deep in the earth, beneath the palace, is the Well. It is a sacred place that few are fortunate to set foot within. The Well is part bathhouse and holy waters; part water supply for the palace above.
Entrance. The winding path carries you deep within the earth. After a long walk, ever downwards the path widens and torches lit with eternal flames are spotted up ahead. Beyond the pillars you see an entryway – the narrow dark path between 2 towering stone pillars, several stories tall.

Bathhouse. The room has strange features – a trough runs around the room and disappears down the hallway to the left. In the center of the room there is a 5 foot deep recessed floor with a small drain in the middle. The walls are intricately carved and a statue stands at the east end of the room. [When activated, hot water runs from the pumping room along the troughs in the floor and fills the bath. Steam rises from the inviting waters.]
Changerooms. A wooden door on the right leads to 4 small rooms, each equipped with a bench and clothing rack.
Main Hallway. Towering Pillars run the length of the hallway. The same troughs run along either side of the hallway. Halfway down on the right the hallway opens up into a large cavern with the sound of a raging waterfall coming from it. Ornate stone doors are visible at the far end of the hall. A non-descript wooden door is tucked at the far end on the right.
The Well / Cavern. The Sacred waters. Water pours in from hundreds of feet above [...the same bridge/waterfall crossed in my Palace Dungeon map]. Stone steps lead into the water before a precipitous drop to the depths hundreds of feet below. A much shallower river exits to the west. Players who investigate the water may discover a large pipe leading to the west [into the pumping room] and a much smaller pipe in the northeast corner [outflow from the treasure room lock]. Within the depths, who knows what they may find? [A mythosaur perhaps]. The northeast corner contains a ledge and small path leading to a mechanically sealed door.

Pumping Room. The ancient pumping mechanisms have been replaced with more recent technology. The cavern outflow river turns a dynamo which powers the pumps lifting water hundreds of feet to the palace above. [Players will need to figure out the right series of switches and levers to be pulled to get water flowing to the room to the south; flipping the wrong switches may turn off the pumps and draw unwanted visitors from the palace above.]
Ceremonial Room. A large altar stands along the south wall and a stone basin in front of it. Troughs run into the walls to the north and east [leading to pumping room and hallway]. The stone basin is intricately carved – once both channels from the pumping room are filled, [*something*] needs to be done to release it to the baths and elsewhere. [Puzzle anyone?].

Treasure Room. The door to this room is mechanically locked. [Only once the pumping room and ceremonial room puzzles are solved will the door be raised using a mechanism hidden deep within the rock]. Beyond sits a chest atop a stone table. [Insert loot here].
Variants. There are a few different variants/stages of this map available. The "standard version" is with the waterfall and none of the puzzles solved. There are [3] variants for various stages of solving the waterworks puzzles (1 channel to ceremonial room; 2 channels and basin filled; completely solved/bath operational). There is also [1] variant for no waterfall if you'd like to slot this map elsewhere in your game (not directly tied to the Palace/Dungeon above) although that does present a slight issue of how the well fills...perhaps it fills from lower down.
Files. The zip files below contain the maps including all variants. Another fun custom map that evolved as I went with new ideas and I hope you like the end result!