thumb|right| Kulgrinda by Medvėgalis hillfort '''''' (plural ; from the Samogitian 'stone' and 'pavement', itself from 'to rake, pull together') is a hidden, usually winding, underwater stony road or ford across swamps, swampy areas, lakes, or along rivers, used as a defense in the lands of Baltic tribes, in particular, in the history of Lithuania. Similar secret roads made primarily of wood and ground were known as '''''' (from , 'tree') and '''''' (from , 'earth, ground') respectively. Old Prussians are known to build kulgrindas already in the first centuries (of Common Era), while the Lithu
thumb|right| Kulgrinda by Medvėgalis hillfort '''''' (plural ; from the Samogitian 'stone' and 'pavement', itself from 'to rake, pull together') is a hidden, usually winding, underwater stony road or ford across swamps, swampy areas, lakes, or along rivers, used as a defense in the lands of Baltic tribes, in particular, in the history of Lithuania. Similar secret roads made primarily of wood and ground were known as '''''' (from , 'tree') and '''''' (from , 'earth, ground') respectively. Old Prussians are known to build kulgrindas already in the first centuries (of Common Era), while the Lithuanian ones are dated to the Middle Ages.
==Function and construction== Undetectable from the surface, these roads were usually known only to the locals, and as such were an important element of the defense against various invaders, including the Teutonic Knights in the 13–14th centuries. Kūlgrindas provided safe shortcuts between villages, hillforts, and other defensive structures. They were built by bringing stones, wood, or gravel over frozen swamps in the winter and letting them sink once the ice melted. Such procedure would be repeated several times. Sometimes wooden posts were inserted to protect the elevated area from washing away.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).