Corpus of symbols produced by the Indus alley Civilization between 3500 and 1900 BCE. Most inscriptions containing these symbols are extremely short, making it difficult to judge whether or not these symbols constituted a script used to record a language, or even symbolise a writing system. There is no known bilingual inscription to help decipher the script, nor does the script show any significant changes over time. (Yeah I just pasted wikipedia here, I have no clue otherwise) Can anyone shed some light here please?
Not to forestall further discussion, but I discussed this in Why haven't we deciphered Indus Valley Civilization script yet or are we any closer?