233670
In the late 16th century , it was a part of the Great Abatis Border and guarded the Ryazhsk portage from the Don to the Oka River .
 Ryazhsk
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Ryazhsk