Visvesvaraya was born near Bengaluru and studied engineering in Pune. He worked in Surat, Bombay, Hyderabad, Aden and Tanzania. In 1909, he was invited to be Chief Engineer of Mysore state. He proposed the Krishna Raja Sagara dam. Though expensive, it was approved by the Mysore Maharaja Krishna Raja Wodeyar. It took 20 years to build was opened in 1931.
He became the Dewan (Prime Minister) of Mysore in 1912 and served the Maharaja. He transformed Mysore into one of the most modern places in India – building industries, universities, power supply, banks etc. He was knighted by the British government & honored with Bharat Ratna by free India.
It is said that on being appointed Diwan, he called his relatives and said that he would accept the appointment only if they swore not to ask for favours. He remains one of the most recognizable figures in Karnataka. Engineer’s day is celebrated in Tanzania and Sri Lanka as well on September 15th honouring his contributions. The image from Wikimedia by Ashwin Kumar is of the majestic Krishna Raja Sagara.

Archaeologists have discovered iron objects at six sites in Tamil Nadu. Nearby charcoal, paddy and ceramic bits have been dated to 1,145–3,345 BCE, or between 3,200 to 5,400 years old. This suggests that the process of extracting, smelting, forging and shaping iron to create tools, weapons and other objects may have developed independently in the Indian subcontinent. Earlier, Gachibowli in Hyderabad had revealed iron from 2000 BCE approximately. The earliest organized iron & steel making began in Turkey dating around 1300 BCE.
Tamil Nadu & South India developed into a great centre of iron & steel. From 1st cent BCE onwards, they developed the famous ‘Wootz’ steel, famed for its ability to be worked into thin blades. It was the raw material for making the world famous ‘Damascus’ swords. Wootz is said to be a mistranslation of the Tamil word ‘urukku’ (alloy) or ‘ukku’ (melt). The North developed its own iron techniques evidenced in the Gupta era rust free iron pillar, now standing near Qutub Minar in Delhi. The image shows the iron objects excavated in Tamil Nadu.
Source: https://www.bbc.com/news/articles/c62e36jm4jro

The grand Anaikut also known as Kallanai is an ancient dam built on the Cauvery river in the State of Tamil Nadu. It was built by the Chola king, Karikalan, around the first century CE. It is considered one of the oldest water diversion or water regulator structures in the world, still in use.
The Kallanai is a massive dam of unhewn stone 329 metres long and 20 metres wide across the mainstream of Cauvery. The purpose of the dam was to maintain higher flow in Cauvery river and to divert floodwaters into the Kollidam river. The dam is still in excellent condition and served as a model to later engineers. Sir Arthur Cotton who built the 19th Century dam across the Kollidam also acknowledged the usefulness of Kallanai. The area irrigated by the ancient irrigation network of which the dam was the centrepiece was 69,000 acres. By the early 20th century, the irrigated area had been increased to about one million acres. The Wikimedia image of the dam is by Beckamrajeev.
Source: Rajya Sabha proceedings, 7 Sept 2007; Question by Shri Tiruchi Siva, DMK

Mauryan polish describes one of the famous characteristics of architecture and sculptures of the Maurya Empire in India (325 to 185 BCE). It gives a very smooth and shiny surface to the stone material, generally of sandstone or granite. Mauryan polish is found especially in the Ashoka Pillars (including our national emblem) as well as in some constructions like the Barabar Caves.
The technique became lost after the fall of Mauryas. According to the archaeologist John Marshall: the “extraordinary precision and accuracy which characterizes all Mauryan works, and which has never, we venture to say, been surpassed even by the finest workmanship on Athenian buildings.”
It is not clear as to how this polish was achieved. The Didarganj Yakshi, sometimes called the ‘Indian Mona Lisa’ for its stunning beauty, is the best example of Mauryan polish. Historians debate whether it was made in the Mauryan period or later, but the polish is distinctively Mauryan.
Source: Wikipedia
Picture Credit: S. R Ramanujam

Rani ki Vav is in Patan, near Mehsana in Gujarat. It is also known for the famous Patan sarees. The stepwell was built by Udayamati in the 11th century in memory of her husband Bhima. It was silted and unknown till 1940s. It is a UNESCO heritage site.
The stepwell is in the shape of an inverted temple and has seven levels. The stairs at each level lead to a circular well at the far end. The stepwell has 500 major sculptures and over a thousand minor sculptures. It has 212 pillars. It also features in our 100 Rs currency note.
Picture Credit: S. R. Ramanujam

The Hoysala era (1026 CE – 1343 CE) was marked by illustrious achievements in art, architecture, and culture, around Hassan in Karnataka. The famous Hoysala temples include the Chennakesava Temple in Belur, the Hoysaleswara Temple in Halebidu, and the Keshava Temple in Somanathapura. These form the 2023 UNESCO World Heritage Site. Many of these temples are still functioning. One feature of Hoysala temples are pillars so shiny & intricate, a finish that cannot be achieved today without lathes. Historians are divided whether these pillars were handcrafted or made with some kind of primitive lathes. We can only marvel at these pillars.
Source: https://whc.unesco.org/en/list/1670/
Picture Credit: S.R Ramanujam

Some ancient south Indian Hindu temples have musical pillars which are made of solid granite. The columns of these musical pillars are often carved from a single piece of granite stone, and they are tuned by means of their length, diameter, and the type of attachment with ceiling and floor. Pillars could be beating pillars where sound is produced by tapping or blowing pillars where sound is produced by blowing wind through holes. These pillars are classified as Shruti which produces basic notes or swaras, Gana produces classical ragas and Laya provides the beats (taal). Experts suggest that the granite used was carefully chosen to be what are called ‘singing rocks’ that have the property of sounding like a bell when struck or rubbing them.
The Wikimedia image by Naveeenkr shows musical pillars at Hampi.
Source: Prasad & Rajavel, ‘Musical Pillars & Singing Rocks’, Stevens Institute of Technology, Hoboken

Firuz Shah Tughlak gets mixed reviews in history. His cruelty & bigotry is known. He also built the massive canal irrigation system around the Indo-Gangetic doab and the region west of the river Yamuna in the 14th cent CE.
Firuz Shah built upon the existing ideas of water conservation. The earlier Chauhan & Tomar rulers of Delhi also invested in baolis & step wells. The still existing Surajkund reservoir is a testimony to their foresight. Ugresan Baoli is in the busy Connaught Place area. Gujarat, Rajasthan, Karnataka & Haryana are known for their excellent artistic stepwells.
Firuz Shah’s canals provided widespread access to water for agricultural lands in northern India in addition to water for the people. In the 1850s, the British built their canal networks on these medieval structures. These works have been further expanded after independence.
The Wikimedia image by Kumarssp shows a baoli in Ferozhah Kotla, Delhi.
Source: ‘Detailed Study of Irrigation Canal’, Sapan Kumar et al, IRJMETS, Dec2022

The ancient roadway links the eastern and western regions of India. It has played a significant role in in the political and economic life of India since the Mauryan period (322 BC–185 BC). The trade route was improved with the road built by Sher Shah Suri. He named it as Sadak-e-Azam (The great road).
The British further improved the road and renamed it Grand Trunk Road. It provided an unbroken line of communication between Calcutta and Peshawar stretching almost over 1,500 miles. Except in case of very wide rivers, the road was permanently bridged throughout.
After Independence, it was abbreviated as NH-1 and NH-2 and named Sher Shah Suri Marg to give due respect to its builder. Sher Shah drove the 2nd Mughal emperor Humayun out of India and ruled from 1540-45. In 1556, Humayun defeated Sher Shah’s successors and reconquered the empire.
The Wikimedia image shows a painting by Ambrose Dudley imagining Sher Shah inspecting the building of the road.
Source: ‘Grand Trunk Road: Continuity & Change’, Dr Nasir Raza Khan, International Journal of Applied Research 2017

Namdang Sila Saku is a bridge cut out from a single solid rock. It is over the Namdang River at Sibsagar, Assam. It was constructed by workmen brought from Bengal during the reign of Swargadeo Rudra Singha in 1703. He is considered the most illustrious of the Ahom kings of Assam. It is 60 mtrs in length and 6.5 mtrs in breadth. It has six culverts. It takes the load of traffic passing through NH37.
Source: https://sivasagar.assam.gov.in/tourist-place-detail/334
Picture Credit: https://www.tripuntold.com/assam/sivasagar/namdang-stone-bridge/

Sawai Jai Singh created the planned city of Jaipur in early 18th cent CE. Sawai Pratap Singh added the Hawa Mahal in 1799. Hawa Mahal is shaped like Krishna’s crown as Pratap Singh was a devotee of Krishna. It is 87 feet high and has 953 ornate louvered windows (jharokas). Few realize that what you see from the street is essentially the rear of the building. The purpose was to allow the royal ladies to enjoy everyday street scenes without being seen. The building created a cool microclimate for the ladies in hot Jaipur. The orientation of the building is on the east-west axis in the direction of wind flow. The wind enters the palace from the west through open grounds and picks up moisture from the water body placed in the courtyard through convection currents. The moisture-laden wind then moves towards the 953 jharokhas and cools the air down via the Venturi effect – air flows through a constricted passage, increasing the wind velocity while dropping the pressure. Hawa Mahal literally means ‘palace of wind’.
The Wikimedia image of Hawa Mahal is by Marcin Bialek.
Source: Hawa
Mahal: How India’s ‘palace of winds’ was ahead of its time | CNN

At Aranmula, a unique mirror making tradition survives. Here a cast bronze of 33% tin is made without lead. It has a highly reflective property comparable to modern mercury coated glass mirrors. Bronze mirrors have been found elsewhere but they have much less tin (25%) and more lead and thus don’t have great reflection.
Ancient India was a great centre for alloys like bronze & brass. The mastery over bronze is reflected in the dancing girl from the 3rd millenium BCE Indus Valley to the 9th- 10th cent CE Chola Bronze Natarajas made from five metals. Greeks from Alexander’s time also observed that Indians had bronze vessels to store food. This requires making bronze with precise 23% tin which needs to be quickly cooled in oil after mixing. If not, the vessel is brittle and also gets oxidized and cannot store food.
Indians made true brass (>30% zinc content) durable ‘pital’ vessels which were considered family heirlooms till a few decades back. This was because at Zewar in Rajasthan, a technique was developed to distil pure zinc on a commercial scale since 9th cent CE. This zinc making appeared in China & Europe many centuries later. Other parts of the world made brass through cementation that had zinc <30%.
Source: You Tube lecture on Indian metallurgy by Dr Anil Suri, Aalborg, Denmark
Picture Credit: Aranmulakannadi.org