History buff uncovers lost medieval monastery thanks to strange map symbol

In a statement translated from Swedish to English, Arkeologerna credited hobbyist Göran Bengtsson with pinpointing the site.

While studying 18th-century maps, Bengtsson noticed a strange rectangle - and brought himself to the site. A surveyor marked the location as "Klosterkullen," or "monastery hill," on a 1760 map.

After an alert from Bengtsson, archaeologists headed out to the location to use ground-penetrating radar (GPR) to scope out the site. GPR can show things hidden in the ground - and it revealed the walls of "probable" monastery ruins.

Archaeologist Bengt Westergaard said the find came as a total surprise to him.

He added, "I have never seen anything like it; the walls were very clearly visible."

The weather conditions helped archaeologists, too. Bengtsson found traces of the monastery on a dry summer day.

"When the ground is dry, something called crop marks can form, and these walls are very visible above ground," he explained. 

"When using ground-penetrating radar, any structures below ground appear as dark spots, and here there was a significant anomaly."

Archaeologists uncovered walls which are roughly 6.5 feet thick, as well as other facets of the building. 

Experts believe the walls were remains of pillar foundations.

"We won't know until we investigate the site further."