Original: It runs  east, underneath Sheppard Avenue from Sheppard station on the Yonge line (now renamed Sheppard-Yonge), to Don Mills station at Sheppard and Don Mills Road.
Simplified: It runs 5.5 km east, under Sheppard Avenue from Sheppard station on the Yonge line (now called Sheppard-Yonge), to Don Mills station at Sheppard and Don Mills Road.