the western terminus of rm 620 is at sh 71 in bee cave in travis county. from there, it travels north through the city of lakeway, following along southeastern lake travis until it crosses the colorado river at mansfield dam near marshall ford. to the northeast, rm 620 enters the city of austin and intersects rm 2222. the road then intersects rm 2769 just inside the williamson county line. to the east, the road travels concurrently with the free service roads of the sh-45 toll road crossing us-183, the 183a toll road, and fm 734 before separating from sh 45 and entering round rock. the road intersects i-35 before terminating at bus. i-35-l in round rock.