One very powerful feature in Context Broker GE is the ability to perform geo-located queries. You can query entities located inside (or outside) a region defined by a circle or a polygon.
For example, to query for all the restaurants within 13 km of the Vitoria-Gasteiz city center (identified by GPS coordinates 42.846718, -2.671635) a Context Consumer application will use the following query:

POST <cb_host>:<cb_port>/v1/queryContext

Headers:

{
  'Content-Type':     'application/json',
  'Fiware-Service':   'tourguide'
}

Payload:

{
  "entities": [
    {
      "type": "Restaurant",
      "isPattern": "true",
      "id": ".*"
    }
  ],
  "restriction": {
    "scopes": [
      {
        "type": "FIWARE::Location",
        "value": {
          "circle": {
            "centerLatitude": 42.846718,
            "centerLongitude": -2.671635,
            "radius": "13000"
          }
        }
      }
    ]
  }
}

To query for all restaurants inside a defined zone inside Vitoria-Gasteiz city a Context Consumer application will use the following query:

POST <cb_host>:<cb_port>/v1/queryContext

Headers:

{
  'Content-Type':     'application/json',
  'Fiware-Service':   'tourguide'
}

Payload:

{
  "entities": [
    {
      "type": "Restaurant",
      "isPattern": "true",
      "id": ".*"
    }
  ],
  "restriction": {
    "scopes":[
      {
        "type": "FIWARE::Location",
        "value": {
          "polygon": {
            "vertices": [
              {
                "latitude": 42.847476,
                "longitude": -2.763969
              },
              {
                "latitude": 42.826006,
                "longitude": -2.743151
              },
              {
                "latitude": 42.826485,
                "longitude":  -2.653740
              },
              {
                "latitude": 42.867061,
                "longitude": -2.630934
              },
              {
                "latitude":  42.881801,
                "longitude":  -2.640617
              },
              {
                "latitude":   42.867767,
                "longitude":   -2.726723
              }
            ]
          }
        }
      }
    ]
  }
}