Yến" stream is a main way to "Huơng Tích" cave. From "Bến Đục", situated next to "Đáy" river, we walked about 1,5 km to "Bến Yến", then take a boat in "Yến" stream about 4 - 5 km to the "Bến Trong".
https://busy.org/@ltn/yen-stream-24
Post and more pictures here!