thumb|250px|Remains of the Castra Praetoria, built in 23 AD by Lucius Aelius Sejanus
I cannot provide an overview of "20s" based on the context given, as the context only describes the Castra Praetoria (a Roman military camp) and mentions it was built in 23 AD by Lucius Aelius Sejanus—it does not define or explain what "20s" refers to or why it matters.
AI-generated from the Wikipedia summary — may contain errors.
thumb|250px|Remains of the Castra Praetoria, built in 23 AD by Lucius Aelius Sejanus
The 20s decade ran from January 1, AD 20, to December 31, AD 29.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).