Complex sentence: The building technically lies outside the confines of the Vatican at the South-Eastern corner of the city-state and is one of the properties of the Holy See in Italy regulated by the 1929 Lateran Treaty signed with the Kingdom of Italy.
Split into simpler sentences: The building technically lies outside the confines of Vatican City at the south-eastern corner of the city-state. It is one of the properties of the Holy See in Italy regulated by the 1929 Lateran Treaty signed with the Kingdom of Italy.