Life
Lucius Annaeus Seneca was born at Corduba in Spain, made a career at Rome, was exiled to Corsica under Claudius, was recalled to tutor the young Nero, and became with Burrus the effective manager of the early years of Nero's reign. He withdrew as his position became untenable and was ordered to take his own life in 65 CE after the Pisonian conspiracy.
The problem his career poses
Seneca wrote on the contempt for wealth while being among the richest men in Rome, on clemency while serving an increasingly murderous emperor, and on the good death while accommodating himself for years to a court that made accommodation costly.
Ancient critics noticed. So did he: several of the letters address the gap between what he recommends and what he manages, and the honesty of that admission is part of why the letters are still read.
This platform does not resolve the tension. It is the most interesting thing about him.
The works
The Letters to Lucilius are the most read: short essays in epistolary form on time, death, friendship, anger and the practice of philosophy as daily discipline rather than doctrine. The dialogues include On Anger, On the Shortness of Life and On Providence. The tragedies — Medea, Thyestes, Phaedra — are extraordinarily violent and were decisive for Renaissance drama.
Why he appears in the architecture layer
For a single letter. In Letters 56 he describes, from the flat above a bath-house, the noise of grunting weightlifters, the slap of the masseur, the shouting of the drink seller and the man who sings in the plunge pool. It is the best surviving account of what a Roman bath actually sounded like, and it comes from a philosopher complaining about the racket while trying to work.