Tinos is an island with many natural treasures. Apart from the peaceful and calm Tinian landscape, there is its wild side, with the rocks, carved by the strong winds and the wild waves. This island has a lot of unexplored caves that capitulated to time and the natural phenomena. The biggest and most important caves of the island are the following:

The cave of "Gastria"
It is located 1 km west of "Kionia" and it is ascertained that some ceramic workshops existed here in the past. The notion is supported by the fact that the soil here is rich in clay, but also by the existence of two firing kilns found here. In addition to that, many ceramic fragments have been found in the area, due to the proximity of the Temple of Poseidon and Amphitrite, which needed ceramic pots for the pilgrim crowds. Moreover, the name "Gastria" possibly comes from the word "Glastria" (clay vessels).
The cave is over 50 m long and its interior dimensions widen considerably in some points. Just behind the cave entrance, a strange circular construction has been discovered. According to tradition, it was here the Christians came to hide and find shelter during the period of their persecution. Some Early-Christian inscriptions have been discovered on the cave walls and they are considered a proof of this fact.
The legend wants this cave to having been connected with the Castle of Xomburgo, through a secret passage. This assumption is almost impossible to prove, since the cave ends abruptly at a certain point, probably due to some rock and earth masses collapsing above. This place is worth being explored further, because it presents both geological and archaeological interest.
 
Mygospilia or Kameni Spilia (Fly-Cave or Burnt Cave)
It is located 6 km west of the village "Aetofolia" and 200 m above sea level, in the area "Kastela". This cave is 55 m long and has two entrances. There are human bones of at least six women and children scattered around. From the clay-pot fragments found here, we can deduct that the remains date back to the Greek revolution and beyond. The tradition says that some destroyer lit a fire at the entrance of the cave and condemned these people to torture and martyrdom. A curious aspect of the cave is the rare species of flies living here in a swarm. Specialists maintain that this fly species exists only here.

"Drakolakas"
It is 4 km far from the village "Platia" and 1 km from "Vathi"- bay. The cave's name comes from "Drakoti" which is a local appellation for the affliction "cyanosis". The locals brought the children affected from the sickness here, and changed their black clothes into colorful ones. They prayed there for their cure and the children stayed in the cave for three nights. The ones that survived were considered to be cured by the healing capacities of the cave.

The cave of "Panormos"
Το σπήλαιο αυτό εντοπίζεται βόρεια του Πανόρµου, στο βορειοδυτικό τµήµα της Τήνου. Ανακαλύφθηκε το 1854 και µετατράπηκε σε λατοµείο εξόρυξης µαρµάρου.

Some of the minor caves of the island are:

The cave of "Vriocastro"
It is located in the southeast side of the pre-historic hill "Vriocastro". It is 4 m wide and its length is about 5m. The access can be achieved only from the sea.

The cave of "Vourlismena"
It can be found near the location bearing the same name, in the eastern part of the island. It is 4 m wide and 5 m deep. Its ground is rocky and it is considered a wild pigeon reservation.

The cave of "Kithara" ("Guitar")
It is 3 km north of the above cave. It got its name from the cove that has the shape of a guitar. It is 5 m wide and 6 m deep. It can be reached only by sea. It is also a reservation for wild pigeons. It is said that this cave is connected to the mountain Tsiknias.