The largest ‘neighborhood’ in the city is, of course, the undercity known as the ‘subterrane’. This is a vast, ancient agglomeration of subterranean works from different cultures and time periods, all of which are now interconnected. The Dortin Peninsula, and in particular the uplands near the city, are on a foundation of porous volcanic rock, which allows the seepage of water to weaken floors, walls, and ceilings, causing passages to appear. This process is supplemented by the purposeful construction of tunnels to link certain features. The shallowest level, usually directly below the streets, are the old Imperial sewers. Dating from the period of heavy Imperial investment in the city’s infrastructure before and after the wars of the fifth century, these pipes, drains and shafts travel everywhere beneath the city, often but not always following the courses of the streets. Even the largest pipes are only 10’ wide and the same tall, and smaller pipes can be only a few inches across. There are several great ‘junction rooms’ at which numerous pipes converge, some of which contain ancient pumping machinery; the largest of these is several hundred feet beneath Alaster Compound. There are manholes at major intersections throughout the city, often intricately crafted works of art, which provide access to the pipes via a 20’ ladder of slippery iron rungs (Balance check DC 15). There are also numerous storm drains built into the curbs, both on major and minor roads; some of these are large enough for a man to slide through on his stomach, especially if they have crumbled, though there will always be a 10’ drop. The sewers emerge into The River Dortin at several points in the southern part of Soldiers’ Beach and beneath Orchard Hill, and into The Big Lake at numerous points in the central docks area and west of the city outside Treetown. During periods of heavy rain, they flood irregularly, in odd ways that seem to have little to do with elevation or hydrography. As a result, the course of stormwater is unpredictable.
In addition to the sewers, there are many other types of feature here, the most common of which are the catacombs. During the periods of war in the city it became a common custom to inter the dead in these chambers, where they would be stored for a number of years, then disarticulated and moved to bone chambers called ossuaries. Because it is therefore generally impossible to locate a specific set of remains, many townspeople have preserved the ancient habit of ‘adopting’ a particular ossuary beneath their neighborhood; one can see them placing flowers on certain sewer grates or tossing them down drains. People also sometimes go into the chambers personally to place offerings. Catacombs are well-distributed throughout the city, and sometimes a single complex might be quite large. Similar to the catacombs are the crypts of individual citizens, which could range from a single room of hewn stone to a complex of several rooms that might include workshops and preparation chambers.
Burrowing animals, especially large ones like The Giant Rat of Dortin, if it exists, make their own paths through the rock and loam under the city. Their tunnels often include small chambers. There are also a few natural caverns left undisturbed, and the watercourses and winding caves that connect them.
At various times in the history of Dortin people have found it necessary to move their lives underground; one unique feature of the city’s subterrane is the presence of whole buildings, such as shops, galleries, homes and amphitheaters, constructed by citizens who needed the safety or privacy of the underground. These almost always have well-planned tunnel systems associated with them, and access points to the city. Similar to these but more spartan are the shelters that were excavated during wartime for the needs of refugees.
The city’s elite have not been missing from the subterrane either. Large structures like Karel Castle invariably have enormous dungeons, and most expensive homes, especially those on Orchard Hill, are surprisingly large beneath the surface. Castles and manors also often have private tunnels that set off long distances across the city, giving a certain person a secret passageway to his lover’s house or his favorite bar.
Almost all buildings in Dortin have basements, even if these are just a root cellar or a cavern where wine or beer is kept cool; those that don’t often have some equivalent feature like a garbage chute that leads down to nowhere, or a well that accesses a cistern beneath the house; these chambers are just as riddled with leaks and passages as the rest of the subterrane.
Any of these features could be found in a state of current use, possibly even well-lit, or it could be abandoned, or even long-abandoned, an ancient ruin. Many areas have been intermittently flooded, or colonized by animals. Many other areas have been suspiciously well-tended, even shored up against collapse, apparently by a skilled individual.
Adventurers wishing to explore the subterrane or use it for transit must surmount several problems. First, they must decide whether to stick to the sewer pipes or set off ‘across country’ as it were. The difference is that by using the great variety of secondary features, an explorer can submerge or emerge virtually anywhere in the city, even within private buildings. By contrast, one who uses the sewers only must submerge and emerge via a storm drain or a manhole. When using the sewers, a Wisdom check DC 15 is necessary in order to move in the right direction, because of their confusing twists and turns; a second Wisdom check at the same DC must be made in order to move the desired distance through the city. These DC’s increase to 20 for characters who are using the secondary features. Drawing a map, which requires a Wisdom check DC 15, can reduce the DC by 5 for that trip only (one point A to one point B). Even maps become useless after a year, by which time the path might have changed. Dwarves apply their +2 stonecunning racial bonus to these checks. When using the secondary features, a traveler can specify specific points of entry and exit and achieve them if the checks are made; but if the checks fail, the point of exit might be wildly unexpected. When using the sewers, the traveler can enter and exit only at manholes and storm drains, which exist in certain locations. In daylight in an inhabited neighborhood, using any manhole for this purpose will certainly be seen by someone on the street. Using a storm drain carries only a 50% chance of being seen. At night, these numbers are halved (50% for a manhole, 25% for a storm drain).
There is a 50% chance of an encounter during any trip beneath the surface.