Blackmarsh is a hexcrawl setting for 0e-compatible games that details the Castle Blackmarsh, 17 geographical sites, and 78 locations. From the introduction:

Blackmarsh was designed to evoke the earliest campaigns of the world’s most popular roleplaying game. It takes place amid a wilderness full of danger and the possibility of great treasure. It is organized as a numbered hex grid with locales keyed to specific hexes. Locales are described briefly in a paragraph or two. Most locales are meant to serve as a springboard for the referee to create his own details. In addition, geographical entities, organizations, and realms that span multiple hexes are described as well.