The Pallava period Rock-cut temples namely Sri Karivartharaja Perumal Temple, Siva Temple and Sri Vedhandheeswarar Cave Temple in Vallam village which is 3 km from Chengalpattu Taluk, Kanchipuram District.
The village goes back to the Pallava period when three cave-temples were excavated on the eastern face of a low hill. Two caves are on same boulder one above the other cave, while the third is located little north of the previous one.
Vasantesvaram Cave-temple is the uppermost and the largest excavation on this hill. The front facade is supported on two pillars and two pilasters. Pilasters follow the pillars in design. Corbel above the pillars is with curved profile. The shrine in the rear has two niches flanking its entrance. Inside the niches are provided dvarapalas. Both dvarapalas are very similar in design and execution with few difference, like southern dvarapala wears his yajnopavita in upavita style while the northern dvarapala is wearing in nivita style.
This difference, in wearing the yajnopavita, is observed at several places, however its objective is still not very clear. An interesting feature of the southern dvarapala is its protruding horns on either side of the headdress. This topic has been discussed in detail in Kuranganailmuttam cave temple article. While in Kuranganilmuttam, we observed an extra protrusion above the headdress, the dvarapala at Vallam clearly shows that the side prongs were not attached to his headdress.
This further substantiate the theory that these horns are the representation of Shiva’s trishula, making dvarapala an ayudha-purusha. Similarly, the northern dvarpala has a protrusion in front of his headdress. Few scholars have suggested this as a chakra however the suggestion from Gift Shiromoney & Michael Lockwood seems most appropriate.
They suggest that this protrusion represents the blade of an axe (parashu), a weapon usually associated with Shiva. Therefore, this dvarpala should be taken as another ayudha-purusha. An excellent and very detailed article on Poetry in Stone explains these features of the dvarapalas in minute details.
There are two small niches, beyond the pilasters of the front row. These niches are not aligned with cave, so it looks that these were excavated later after excavation of the cave.
Source : puratattva