extern std::map<level_pos, std::string> portal_vault_notes;

    marshallMap(th, portal_vault_notes,
                marshall_level_pos, marshallStringNoMax);

    unmarshallMap(th, portal_vault_notes,
                  unmarshall_level_pos, unmarshallStringNoMax);

typedef std::map<level_pos, std::string> portal_note_map_type;

portal_note_map_type portal_vault_notes;

                if ( ci_portals->first.id == last_id )
                    disp += '*';

                const level_id  lid   = ci_portals->first.id;
                const level_pos where = ci_portals->first;
                if ( lid == last_id )
                {
                    if (!portal_vault_notes[where].empty())
                    {
                        disp += " (";
                        disp += portal_vault_notes[where];
                        disp += ")";
                    }
                    else
                        disp += '*';
                }

                    disp += ci_portals->first.id.describe(false, true);

                    disp += lid.describe(false, true);
                    if (!portal_vault_notes[where].empty())
                    {
                        disp += " (";
                        disp += portal_vault_notes[where];
                        disp += ") ";
                    }

                last_id = ci_portals->first.id;

                last_id = lid;

    (void) find_erase(portal_vault_notes, pos);

        portal_name = env.markers.property_at(pos, MAT_ANY, "dstovermap");

        portal_name = env.markers.property_at(pos, MAT_ANY, "overmap");

        portal_vault_notes[where] =
            env.markers.property_at(pos, MAT_ANY, "overmap_note");

                                     dstovermap = "glowing drain",

                                     overmap = "glowing drain",

                                     dstovermap = "frozen archway",

                                     overmap = "frozen archway",

      overmap = "Ziggurat",
      overmap_note = "" .. entry_fee .. " gp",

      dstovermap = "Ziggurat",

with the "dstovermap" parameter.

with the "overmap" parameter.  A note can be made to accompany the
portal's position on the overmap with the "overmap_note" parameter.