On the northern outskirts of Jaffna, in the Puttur area of the Valikaamam East division, a collapsed limestone cavern has been drawing curious visitors for well over a century. Known locally as the Nilavarai Well — and colloquially as the "bottomless well" — it is one of the most geologically intriguing sites in northern Sri Lanka. Despite the name, it does have a bottom; what it has in abundance is mystery.
What is the Nilavarai Bottomless Well?
The well was not dug by hand in the conventional sense. It formed when the surface crust above a natural limestone cavern collapsed, exposing an underground chamber connected to a subterranean water source. The opening measures roughly 25 feet in length and 40 feet in width — large enough to feel more like a sunken pool than a domestic well. A flight of stone steps descends to the water surface, which sits around 14 feet below ground level.
The water in the upper portion is fresh. Farmers in the surrounding area have long depended on it, and the well is said never to run dry — even during prolonged droughts. Below a depth of roughly 40 to 60 feet, however, the water becomes brackish and eventually saline, which points to a connection with the sea or tidal aquifers below.
What does science say about the well?
The earliest systematic investigation of Nilavarai on record was published in the 1865–66 edition of the Journal of the Ceylon Branch of the Royal Asiatic Society of Great Britain and Ireland. Researchers collected water samples at depths of 45 feet, 95 feet, and 145 feet using sealed valve instruments and shipped them to England for chemical analysis. The results showed that the well was definitively not bottomless — it had a floor at approximately 145–150 feet — and that brackishness began between 40 and 50 feet. A distinct smell of hydrogen sulphide was detected in samples taken from near the bottom.
The same expedition also investigated the popular belief that the water level rises and falls in sync with the tides. Researchers measured water levels at the Jaffna Lagoon, the Valvettithurai coast, and the Nilavarai well at half-hourly intervals from 6 am to 6 pm. The coastal levels fell from around 6:30 am and began rising around 2:00–2:30 pm — the classic twice-daily tidal pattern. The Nilavarai well, however, fell at 6:30 am, rose again at 9:30 am, and fell once more after 2:00 pm: three cycles in a single day against the sea's two. The connection to tidal movement was disproved, but the cause of the triple fluctuation was never resolved and remains unexplained.
What did modern explorers find?
About 150 years after the Victorian-era study, Sri Lanka Navy divers equipped with an automated diving robot conducted a more thorough expedition. Their findings revised the earlier estimates: the well bottom lies at approximately 52.5 metres (172 feet) below the water surface, deeper than the 19th-century probes had reached. Fresh water occupies the first 18.3 metres (roughly 60 feet), beyond which salinity increases progressively. The divers also reported discovering a horizontal tunnel-like passage near the base, which may help explain how external water enters the chamber — though the full extent of that underground network has not yet been mapped.
Is the Nilavarai well connected to Keerimalai?
Local tradition holds that the Nilavarai well is hydrologically linked to the Keerimalai freshwater spring pool on the northern coast, approximately 10 kilometres away. The most often-repeated story claims that a lime fruit dropped into the well has been found floating at Keerimalai. No controlled scientific test of this claim has been published, and the differing water chemistry of the two sites makes a direct open channel unlikely — though an indirect connection through the regional limestone aquifer system cannot be ruled out. The navy expedition found no definitive evidence of a direct passage to Keerimalai, but the underground geology of the Jaffna Peninsula remains incompletely surveyed.
Why was scientific study of Nilavarai delayed?
The Jaffna Peninsula was severely affected by Sri Lanka's civil conflict, which effectively restricted civilian research and tourism in the north for nearly three decades. Following the end of the conflict in 2009, access has steadily improved, and the region's natural and cultural sites — including Nilavarai — have begun attracting researchers and travellers once again. The navy expedition described above was one of the first systematic modern investigations of the well.
How do I get to the Nilavarai Bottomless Well from Jaffna?
The well is located in Puttur, within the Navakkiri Grama Seva area of Valikaamam East — roughly 10 to 15 kilometres south-east of Jaffna town. The most practical way to reach it is by hiring a private car or a tuk-tuk from Jaffna. The approach road passes through flat agricultural land typical of the peninsula, and the site itself is modest in scale: there is no large visitor complex, which gives it a quietly authentic character. Allow around half a day if you plan to combine it with other Jaffna attractions such as Keerimalai or the Nallur Kandaswamy temple.
What should visitors know before going?
- The site is open to the public and there is typically no admission charge, though this can change during local festival periods.
- The steps down to the water level can be slippery — wear footwear with grip.
- Swimming in or entering the well is not permitted.
- The surrounding area is predominantly Tamil-speaking; basic Tamil or Sinhala phrases are helpful, though younger residents in Jaffna town often speak English.
- Early morning visits are cooler and tend to be quieter.
- Combine the visit with the Keerimalai freshwater pools and Casuarina Beach for a fuller day on the Jaffna Peninsula.
What makes Nilavarai geologically significant?
The Jaffna Peninsula sits on a flat limestone platform, and karst features — caves, sinkholes, and underground drainage systems — are a natural consequence of that geology. Nilavarai is one of the more dramatic surface expressions of this karst landscape: a place where the boundary between freshwater aquifer and the surrounding saline sea manifests visibly in a single shaft. The triple daily fluctuation in water level, still unexplained after 160 years of intermittent study, makes it a site of genuine scientific interest beyond its folklore. For geologists studying freshwater-saline interface dynamics in limestone environments, the Jaffna Peninsula as a whole — and Nilavarai in particular — represents an under-researched field site.
For travellers, the well offers something rarer than a polished heritage monument: a natural phenomenon that has puzzled scientists for generations and continues to resist complete explanation. Its understated setting, far from the well-trodden tourist circuit, makes it one of those places that rewards the curious far more than the casual visitor.