return is_travelable_stair(grd(c));

    // Branch entries, portals, and abyss entries are not considered exit
    // stairs here, as they do not provide an exit (in a transitive sense) from
    // the current level.
    switch (grd(c))
    {
    case DNGN_STONE_STAIRS_DOWN_I:
    case DNGN_STONE_STAIRS_DOWN_II:
    case DNGN_STONE_STAIRS_DOWN_III:
    case DNGN_ESCAPE_HATCH_DOWN:
    case DNGN_STONE_STAIRS_UP_I:
    case DNGN_STONE_STAIRS_UP_II:
    case DNGN_STONE_STAIRS_UP_III:
    case DNGN_ESCAPE_HATCH_UP:
    case DNGN_EXIT_HELL:
    case DNGN_RETURN_FROM_ORCISH_MINES:
    case DNGN_RETURN_FROM_HIVE:
    case DNGN_RETURN_FROM_LAIR:
    case DNGN_RETURN_FROM_SLIME_PITS:
    case DNGN_RETURN_FROM_VAULTS:
    case DNGN_RETURN_FROM_CRYPT:
    case DNGN_RETURN_FROM_HALL_OF_BLADES:
    case DNGN_RETURN_FROM_ZOT:
    case DNGN_RETURN_FROM_TEMPLE:
    case DNGN_RETURN_FROM_SNAKE_PIT:
    case DNGN_RETURN_FROM_ELVEN_HALLS:
    case DNGN_RETURN_FROM_TOMB:
    case DNGN_RETURN_FROM_SWAMP:
    case DNGN_RETURN_FROM_SHOALS:
    case DNGN_EXIT_PANDEMONIUM:
    case DNGN_TRANSIT_PANDEMONIUM:
    case DNGN_EXIT_ABYSS:
        return (true);
    default:
        return (false);
    }

    // [enne] - this is not a perfect check.  It's possible that a region
    // could have a single staircase that leads to another a region on
    // another level with a single return staircase.