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 Madrid city center (identified by GPS coordinates 40.418889, -3.691944) a Context Consumer application will use the following query:

POST <cb_host>:<cb_port>/v1/queryContext
{
    "entities": [
        {
            "type": "Restaurant",
            "isPattern": "true",
            "id": ".*"
        }
    ],
    "restriction": {
        "scopes": [
            {
                "type": "FIWARE::Location",
                "value": {
                    "circle": {
                        "centerLatitude": "40.418889",
                        "centerLongitude": "-3.691944",
                        "radius": "13000"
                    }
                }
            }
        ]
    }
}