hydepark = db.poiConcat.findOne( {
  ts: { $all: [
    "name=Hyde Park", "leisure=park"
  ] }
} );

db.poiConcat.find( {
  *l: { $geoWithin: {*
    *$geometry: hydepark.l*
  *} },*
  ts: "amenity=cafe"
} );

{
  "_id" : "w19851241",
  "ty" : NumberLong(2),
  "l" : *{*
    *"type" : "Polygon",*
    *"coordinates" : [*
      *[ [ -0.1549378, 51.508331 ], … [ -0.1549378, 51.508331 ] ]*
    *]*
  *},*
  "ts" : [
    "access=yes", "leisure=park", "name=Hyde Park",
    "wikipedia=http://en.wikipedia.org/wiki/Hyde_Park,_London"
  ]
}