Largest empires in history including all claims on land and sea.
Criteria:1. Claims must be internationally recognized (e.g., papal bulls, treaties).
2. Sea claims ('mare clausum' doctrine) are included. 
3. Only explored and mapped areas are included.
4. Unexplored, but encircled by explored areas (e.g. Australia) are included.
5. Effectively unconquerable territories held by great powers(e.g. Asian kingdoms) are excluded.

Base map: https://commons.wikimedia.org/wiki/File:Oceans_base_map.svg

Mare clausum description: https://en.wikipedia.org/wiki/Mare_clausum
Own work
Nagihuin