Near Warsaw, where the Narew river and the Vistula meet, you can find a ruins of Modlin Fortress Granary. Nowadays the place is totally ruined, and quite dangerous, but is still worth to see. The building erected in the 19th century was bombed during WW2. Fortunately, mort of the walls survived and today we can admire these beatuiful ruins. How do they look like? Just check the photos below 
:
:
