The Areopagus is sandwiched between the agora and the Acropolis.

You can reach the Areopagus from either the Acropolis (Line #2) or the Thissio (Line #1) stations. If you use the Acropolis Station, find Dionissiou Areopagitou Street and head uphill (west) until you crest the hill. Look for a road winding up to your right. Follow this for about 30-40 yards and start looking for the Areopagus on your left. If you use the Thissio Station, find Apostolou Paulou Street and (again) walk uphill (south) until you reach the crest. Look for the same road winding up the hill (only, from this direction, the road will be on your left).

The Areopagus is right next door to the Acropolis itself. When in doubt, follow signs to the Acropolis. If you find yourself at the western entry gate to the Acropolis, you’re just a stone’s throw from the right spot. Just wander downhill (north) to the Areopagus.