[{"_id":ObjectId("574ffe9bda461e4b4b0043ab"),"list1":[{"_id":"54","list2":[{"lang":"EN","value":"val1"},{"lang":"ES","value":"val2"},{"lang":"FR","value":"val3"},{"lang":"IT","value":"val3"}]}]}]

db.collection.aggregate([{$unwind:"$list1"},{$match:{"list1._id":"54"}},{$unwind:"$list1.list2"},{$match:{"list1.list2.lang":"IT"}},{$project:{_id:"$list1._id",val:"$list1.list2.value"}}])