The Indus Valley held one of the earliest urban civilisations on earth, with planned cities at Mohenjo-daro and Harappa, standardised brick sizes, drainage in the streets and a script on thousands of small seals. It also holds the clearest example in this atlas of how much cannot be said.
What survives is suggestive. A large watertight tank at Mohenjo-daro, surrounded by rooms and reached by steps at either end, is usually called the Great Bath and is generally taken to have served some collective purpose involving water. Seals show a figure seated with legs drawn up and a horned headdress, which John Marshall in the 1931 excavation report identified as a prototype of Shiva as lord of animals, an identification that has been argued about ever since and is now widely treated as unproven. Terracotta female figurines are numerous; whether they are goddesses, toys or something else is not established. No building has been securely identified as a temple, and no burial suggests a ruler treated as divine.
The obstacle is the script. It survives only in very short inscriptions, mostly of a few signs, with no bilingual text and no agreement on what language it records or even whether it records a language at all. Until that changes, statements about Harappan religion are inferences from objects, and the atlas records them as inferences.