The Adriatic Sea (アドリア海 Adoriakai?), Mare Adriatico in Italian, is a large body to the east of Italy, separating the Italian Peninsula from the Balkan peninsula and the Apennine Mountains from the Dinaric Alps and adjacent ranges.
The sea is the site of the engagement between Amakusa-Style Remix of Church led by Tatemiya Saiji and the Roman Catholic Church lead by Biagio Busoni on the flagship of the La Regina del Mare Adriatico.
The Adriatic is an important body of water to its inhabitants. Venice is referred with several titles that points to its connection of with the Adriatic, such as the Water Capital, Queen of the Adriatic Sea, and Bride of the Adriatic Sea. This is because Venice was originally a marine military state controlling the Adriatic Sea. According to Orsola Aquinas, every year, Venice would have a national-level "wedding with the sea" ceremony. At that time when it was still its own country, the ruler of the country would throw a gold ring into the Adriatic Sea to symbolize the merging of Venice and the Adriatic Sea and be closer to it.
Moreover, even La Regina del Mare Adriatico is named after the sea, and many of its ships are formed from the waters of its sea.
- Toaru Majutsu no Index Light Novel Volume 11 Chapter 1 Part 2