Lokrum is an island in the Adriatic Sea 600 metres from the city of Dubrovnik, Croatia. It stretches from northwest to southeast and receives regular ferry service from the city.
Austrian archduke Maximilian once had a holiday home on the island. A monastery and a botanical garden survive from his era. On the island's highest point at 96 metres above sea level stands Fort Royal Castle, which was built by the French during Napoleon's occupation of Croatia, though it was later named "Maximilian's Tower" by the Austrians.
Wikipedia https://en.wikipedia.org/wiki/Lokrum
Official website http://www.lokrum.hr
Coordinates 42°37'38.763" N 18°7'11.423" E