Shinespark into the slope at the foot of the door and run through back to the tall shaft. Duck at the end to charge up the Speed Booster, then quickly jump down and open the door leading back into the Map Room. Run to the far right end of the roof section, then begin running back left.
You can break up into the roof section to bypass the enemies along the floor, but you'll also be able to use it to build up the Speed Booster's charge. Enter the next corridor to find a ridiculously long hallway. Descend the shaft containing the previous Missile Tank and head right to find the Map Room.
This Missile Tank along with RI.03 reside in the same room, but reaching both can be tricky.
