True. The architectural accomplishments of the Ancient Indians aren't commonly known. However, their main achievement is among the most sophisticated in the ancient world. Their greatest architecture lies within their cities. dating back to about 3000 BC.
Ancient India (commonly known as the Indus Valley civilization) was one of the first, if not, the only civilization in the ancient world to build cities. Collectively, the Indus Valley civilization is known as the first urban civilization. The greatest feat of this civilization is not that they built cities, but how they built cites. Using grid-like templates, cities were planned on small models and drawn out before they were built. These are the first signs of urban planning and civil engineering. No other civilization had developed such a system.
Indian architects successfully planned almost every detail within a city. Everything including offices, houses, markets, religious buildings, and even public baths (similar to Rome) were planned. This architectural technique is similar to the modern world, which is probably why we consider it so sophisticated. Also, in history they developed and largely used an extensive drainage system, which can only be paralleled by the aqueducts of Rome. With these two advancements, the cities in India, especially Mohenjo-Daro, became outstanding marvels because urban planning complemented the innovative drainage system and vice versa. The Indus Valley civilization emerged to be unique in architecture as they made their own mark and contributed to modern society.