AI overview
I don't have enough context from the single word "decade" to write an accurate overview of "20s BC." To provide a factual, 2-sentence explanation of what "20s BC" is and why it matters, I would need more information about the specific historical, cultural, or other significance you're referring to.
AI-generated from the Wikipedia summary — may contain errors.
Article
Augustus becomes Roman Emperor in 27 BC. This arch, the Arch of Augustus, was erected in 25 BC to celebrate the Roman victory over the Salassi.
The 20s BC were the period 29 BC – 20 BC.