Complex sentence: Running down through Eastern Stara Planina, Kamchiya meanders through the "Longoz" ot longose grove, a UNESCO-protected biospheric reserve protecting the remaning forest from intensive logging that had decimated it by mid- 20th century.
Split into simpler sentences: Running down through Eastern Stara Planina, Kamchiya meanders through the "Longoz" ot longose grove forming a UNESCO-protected biospheric reserve. The reserve preserved the remaning forest from intensive logging that had decimated it by mid- 20th century.