Batu paras volcanic stone stepped tower plinths (known in Balinese as bataran) form the monumental foundational base of the Bale Kulkul drum tower. Built of porous volcanic tuff (batu paras) and red terracotta bricks laid in stepped horizontal terraces, these massive masonry pedestals raise the wooden drum pavilion above ground dampness and floodwaters. Sculpted with high-relief apotropaic iconography—including the protective earth turtle Bedawang Nala, intertwined Nagas, and fierce Bhoma monster heads—the plinth provides the heavy gravitational ballast essential for wind and earthquake stability.
At a Glance: Key Takeaways
- Masonry Material: Batu Paras volcanic tuff & bata merah (terracotta brick)
- Plinth Structure: Stepped pyramidal terraces (Bataran) with rubble-concrete core
- Iconographic Motif: Bhoma monster face, Bedawang Nala (cosmic turtle), Naga serpents
- Plinth Height Range: 2.0 m to 4.5 m above surrounding temple courtyard
- Structural Function: Seismic ballast, moisture elevation, and column footing anchors
The Geological Tectonics of Balinese Batu Paras
Rising from the fertile alluvial plains of central and southern Bali, the architecture of the island is deeply tied to its active volcanic geology. Mount Batur, Mount Agung, and Mount Bratan have blanketed the island across millennia with layers of volcanic ash, pumice, and pyroclastic sediment. In river gorges and valley walls, this compacted volcanic ejecta formed batu paras (volcanic tuff)—a soft, lightweight, fine-grained stone that has served as the sacred sculptural medium of Balinese civilization for over a thousand years.
Batu paras possesses unique working qualities: when newly exposed in quarry faces along the Ayung or Oos rivers, it is saturated with groundwater ('quarry-sap') and so soft that it can be carved like dry clay using simple iron knives and wooden gouges. Upon exposure to atmospheric carbon dioxide and sunlight, the silica and calcium silicates in the tuff carbonate and case-harden, forming a resilient outer crust. Combined with alternating bands of deep terracotta clay bricks (bata merah), this volcanic stone creates the iconic warm, earthy polychromy of Balinese sacred masonry.
Cosmological Foundation: The World Turtle Bedawang Nala
In Balinese architectural philosophy, the foundation plinth (bataran) is never treated as a mute concrete slab; it is an active sacred entity representing the underworld (bhurloka or nista). The base of the Bale Kulkul represents the cosmic origin of the universe as codified in the ancient creation myth of the churning of the cosmic ocean (Samudra Manthana).
Carved around the lower stepped terrace is Bedawang Nala, the primordial cosmic turtle who carries the entire weight of the physical universe upon its shell. Binding the turtle are the two great cosmic serpents: Naga Anantaboga (symbolizing the physical earth and fertile soil) and Naga Basuki (symbolizing water, prosperity, and the eternal flow of life). By incorporating these powerful mythological guardians into the base masonry, the master builder creates an architectural anchor designed to calm the volatile volcanic energies of the Pacific Ring of Fire, spiritually insulating the tower above from ground tremors.
The Guardian Bhoma Mask: Apotropaic Threshold Defense
Dominating the upper tier of the plinth, directly centered above the narrow entrance staircase leading to the drum pavilion, looms the colossal carved face of Bhoma (also known as the Kala head). Born of the union between the earth goddess Dewi Pertiwi and the great god Vishnu, Bhoma is the fierce Lord of the Forest and Guardian of Sacred Thresholds.
Master stonecutters carve Bhoma with wide, terrifying bulging eyes, protruding fangs, an outstretched tongue, and clawed hands grasping wild floral foliage (patra punggel). The mask is an apotropaic device—a spiritual lightning rod engineered to frighten and neutralize malevolent demonic spirits (bhuta kala) who might attempt to ascend the stairs and desecrate the sacred drum chamber. Placed high above human eye level, the fierce countenance of Bhoma reminds anyone entering the tower of the sacred boundary separating the mundane earthly realm from the divine aerial sphere.
Seismic Stability and the Umpak Pedestal Pads
Beyond its spiritual and sculptural grandeur, the stepped batu paras plinth is an engineered seismic ballast structure. Because Bali lies along a violent subduction zone prone to frequent high-magnitude earthquakes, constructing a tall, slender tower presents severe structural risks. The stepped pyramidal configuration of the plinth lowers the building's overall center of gravity, spreading dead loads across a broad foundation footprint that resists overturning moments.
At the top of the stone plinth, builders install monolithic column pads known as umpak. Sculpted from dense, unyielding volcanic andesite (batu candi) in the form of blooming lotus blossoms, these pads serve as isolated friction bearings. The wooden columns of the drum pavilion rest freely on top of the umpak pads without steel anchor bolts or mortar. In the event of an earthquake, the wooden superstructure can rock and slide slightly upon the stone pads, isolating the flexible timber frame from the violent high-frequency ground accelerations of the masonry base and preventing catastrophic structural fracture.
Balinese Plinth Masonry Tiers & Sculptural Details
Use this reference table to calculate exact physical dimensions, ratios, and specifications before purchasing:
| Plinth Level | Material Used | Dimensional Profile | Carved Iconography | Mechanical Role |
|---|---|---|---|---|
| Tepas (Sub-base) | Dense Basalt River Stone | Wide stepped footing (4x4m to 6x6m) | Unadorned or simple torus moldings | Spreads structural weight across foundation soil |
| Batur (Main Plinth) | Batu Paras & Red Brick | Stepped vertical terrace (1.5–2.5m high) | Bedawang Nala turtle flanked by Nagas | Represents the subterranean underworld foundation |
| Palemahan (Upper Tier) | Fine Batu Paras Kerobokan | Molded cornice with dentils | Patra floral arabesques & winged lions | Supports observation floor and stone column bases |
| Umpak (Pedestal Pads) | Monolithic Hard Andesite | Carved lotus blossom (padma) cups | Concentric circular lotus petals | Isolates wooden columns from ground dampness |
| Undag (Ascent Stair) | Basalt Steps with Paras Cheeks | Steep 60° access stairway | Makara sea-monster balustrades | Provides access to the elevated drum pavilion |
Practical Constraints
Every successful decoration project must account for physical and environmental constraints:
Porous, friable nature of volcanic tuff when exposed to biological algae and fungal growth
Tropical moisture fosters black mold and green lichen that obscure delicate sculptural carvings. Mitigation: Wash stone periodically with neutral biological washes and ensure unobstructed solar exposure.
Intense seismic shear stresses acting on stepped masonry terraces during earthquakes
Unreinforced stone veneer can peel away from the interior masonry rubble core. Mitigation: Install stainless steel or copper tie cramps connecting facing stones deeply into the solid rubble core.
Execution Blueprint & Craftsmanship Sequence
Execute this professional sequence to achieve flawless results without backtracking:
Subsoil Excavation & River Stone Footing
Excavate the square foundation pit down to solid volcanic hardpan, filling with compacted river gravels and laying massive basalt boulders in slaked lime mortar.
Setting the Primary Terracotta-Paras Course
Erect the lower stepped terrace (tepas), alternating horizontal bands of deep red clamp-fired clay bricks (bata merah) with soft grey volcanic tuff blocks.
Rubble Core Pouring & Tamping
Backfill the space between outer stone leaves with a dense hydraulic concrete mix composed of crushed volcanic rock, volcanic pozzolan ash, and slaked lime putty.
Upper Tier Stepping and Water Table Dressing
Step the second terrace inward by 300 mm, tooling a continuous chamfered water table (lelempeng) around the perimeter to shed rainwater cleanly.
Sculpting the Bhoma Mask Over the Portal
Carve the monumental head of Bhoma—complete with bulging eyes, fierce fangs, and flaming hair—out of monolithic soft paras blocks centered above the stair.
Relief Carving of Flanking Patra Arabesques
Carve intricate Balinese floral arabesques (patra punggel and patra sari) along the plinth frieze using curved gouges and wooden mallets.
Monolithic Umpak Column Pad Positioning
Carve monolithic lotus-shaped stone pedestals (umpak) from hard volcanic andesite, bedding them with laser-level precision directly above the structural core.
Drainage Weep Holes and Final Wash
Drill concealed 20 mm downward-angled weep holes in terrace corners to evacuate trapped rainwater, washing the stone clean with natural soapnut extract.
Common Mistakes & Countermeasures
Avoid these costly errors that compromise aesthetics, ergonomics, and budget:
Using soft, riverbed batu paras with high clay content for external structural corners
Bonding exterior stone veneer directly with rigid modern Portland cement mortar
Project Execution Checklist
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Frequently Asked Questions
Why is the base of a Balinese drum tower built of stone while the top is built of wood?
This material dichotomy reflects both engineering logic and spiritual cosmology (Tri Angga). Structurally, a heavy stone base anchors the tower against overturning moments caused by high tropical winds, while a lightweight wooden pavilion keeps the top-heavy mass low during earthquakes. Spiritually, stone belongs to the earthly/underworld sphere (nista), while wood and thatch belong to the human (madya) and celestial (utama) realms.
What is the mythological significance of the Bedawang Nala turtle carved at the base?
In Balinese Hindu mythology, the world rests upon the back of a colossal cosmic turtle named Bedawang Nala, who is encircled and bound by two giant world serpents, the Nagas Anantaboga and Basuki. Carving Bedawang Nala at the base of the tower anchors the building symbolically to the stable center of the earth, protecting it from volcanic eruptions and earthquakes.
How do stone carvers prevent carved volcanic tuff from eroding in the monsoon rain?
Traditional carvers design reliefs with steep, self-shedding vertical planes, avoiding deep horizontal ledges where water can pool. Furthermore, the natural colonization of microscopic black lichen and algae forms a biological crust that, while darkening the stone, actually shields the underlying soft volcanic silicate minerals from direct acid-rain weathering.
