matrix-spec/event-schemas/examples/m.room.message#m.location

{
  "age": 146,
  "content": {
    "body": "Big Ben, London, UK",
    "geo_uri": "geo:51.5008,0.1247",
    "thumbnail_url": "mxc://localhost/FHyPlCeYUSFFxlgbQYZmoEoe",
    "thumbnail_info": {
      "mimetype": "image/jpeg",
      "size": 46144,
      "w": 300,
      "h": 300
    },
    "msgtype": "m.location"
  },
  "event_id": "$143273582443PhrSn:localhost",
  "origin_server_ts": 1432735824653,
  "room_id": "!jEsUZKDJdhlrceRyVU:localhost",
  "type": "m.room.message",
  "sender": "@example:localhost"
}