By 2500 BCE, what did the Harappa civilization develop that would not be seen again for 3000 years

By 2500 BCE, what did the Harappa civilization develop that would not be seen again for 3000 years  is discussed below in detail.

Explanation:

Based on the situations that leftover by this civilization, Archeologist mentioned that there are most suitable chambers utilized for indoor baths. Not all structures remained in these baths. Archeologists supposed that it's only shared among the upper-class segments of Harappan civilization.

Estimating from the measurement of the bathrooms, it is strange that they're practiced for a private bath. It's more proper for some kind of association setting like for mistresses to treat a noble. This kind of bathroom did not endure in other civilizations in that age. The most familiar ones were discovered in the Roman empire in around 390 AD.