From SuspireWiki

The Area

Martin Causeway sucks. Literally. Initially, Carcosa city planners intended to build up the bog-ridden area of the city, but the city wasn't having any of that. Any sand and dirt and cement they put down to try and cover up the salty seawater bogs broke up within a year and sunk down into the city. Millions of dollars were wasted in trying to expand into this area of the city before investors and business proposals finally stopped.

Now, Martin Causeway has a market for camp grounds and individuals who like to bird watch or camp without going too far into the wilderness (as with Papal Forest - but that place is creepy as hell anyway). RV parks and small motels are about the only thing in the area. There are some native "guides" for the bogs, but they're mostly a sham. There's only about five separate bogs worth any note, and they're easily found on any map.