MapCraft HQ

D&D Sewer Map Generator

Every city adventure ends up underneath the city. Roll a sewer with channels of murky water flanked by stone walkways, flooded cisterns, a smugglers’ cache and the thing that lives in the deep pool.

Drawing the map…

Pick Paint, Add prop or Remove to edit the map. Keys: N new · D download · G grid · Ctrl Z undo

Size & seed

16–60 squares a side. The same seed, type and size always rebuild the same map.

Export for your table

Map key

A blank grid has no key yet. Paint some rooms and place props, and the read-aloud writer will describe what you drew.

Read-aloud writer

Turns this layout into boxed text to read at the table, plus three tactical hooks. Uses AI; the map itself never needs it.

Quick answer: Press New sewer to roll a city sewer on 5-ft squares: water channels with a walkway on each side, chambers off the main runs, a ladder up to the street and a lair around a central pool. Download it as PNG or as .dd2vtt for Foundry VTT.

How the sewer is built

The generator lays out chambers and connects them like a dungeon, then turns every corridor into a 5-ft channel of water with a stone walkway on either side. Chambers become cisterns, junctions held up by pillars, collapsed tunnels or a smugglers’ cache. The furthest chamber is the lair: a cistern built around a deep pool.

Three ways to use this map

  1. The thieves’ guild pays the party to clear out whatever is eating its smugglers.
  2. A child’s toy floats past on the current, which runs the wrong way.
  3. The wererats have a deal with the city watch, and the party just broke it.

Who lives here? Giant rats (CR 1/8), swarms of rats (CR 1/4), wererats (CR 2), a gelatinous cube (CR 2) or an otyugh (CR 5) in the lair pool. Check the difficulty for your party in the encounter builder, then use the read-aloud writer under the map for boxed text.

Questions game masters ask

What creatures live in D&D sewers?

Giant rats, swarms of rats, wererats, an otyugh in the deepest pool and gelatinous cubes in the tunnels are the classic sewer residents. All are in the free SRD.

Is sewer water difficult terrain?

Shallow channel water is usually run as difficult terrain, which costs 1 extra foot per foot moved. If it is deep enough to swim, swimming also costs 1 extra foot per foot without a swim speed.

How do I connect the sewer to a city map?

The access chamber has a ladder up to a street grate. Mark a matching grate on your city map, and use the seed so you can rebuild the same sewer later.

More tools for your prep

Map generators by location