In the hills above Marathi village, about five kilometres east of Parikia, you can walk into the ancient marble quarries that made Paros famous across the ancient world. The tunnels are dimly lit by oil lamps — the same lamps the ancient miners used, because the passages are too narrow and winding for sunlight to penetrate.
The experience is eerie and genuinely impressive. At one point you squeeze through a gap barely wide enough for a person, which opens into a vaulted chamber where the marks of ancient chisels are still clear on the white walls. A bas-relief of the Nymphs carved into the rock near the entrance is one of the better-preserved ancient reliefs you will find anywhere.
The quarries are unguided; you walk in with a torch or rely on the fixed lights. They close at dusk. There is no admission fee, but bring good shoes — the floor is rough and sometimes wet.