かつて、この場所には三宅村という村の役場があったようです。
大阪府三島郡三宅村。
市町村合併で、村の北側が茨木市、南側が摂津市になりました。
ジオキャッシングとあわせて、記念碑探しもやってみては？
It seems that there used to be a village office called Miyake Village in this place.
Miyake Village, Mishima-gun, Osaka Prefecture.
With the municipal merger, the north side of the village became Ibaraki City and the south side became Settsu City.
Why don't you try looking for a monument along with geocaching?