These ruins - consisting of a single wall and a broken-down part of a tower - are all that remains of a once astounding 13th-century Franciscan monastery. It is hidden away at the very center of the Margaret island.
Wikipedia https://hu.wikipedia.org/wiki/Ferences_kolostor_(Margit-sziget)
Official Website http://muemlekem.hu/muemlek/show/1195?logsall=1
Address (Unnamed Road), Budapest 1007, Hungary
Coordinates 47°31'31.173" N 19°2'47.783" E