Trinity is a walled four-hundred-year-old college dropped in the middle of a working city, and the wall is the whole point: step through the front gate off College Green and the traffic noise falls away as if someone turned a dial. Walk it in the morning before the tour groups thicken.
Through the arch you land in Parliament Square, cobbles underfoot and the Campanile dead centre — students swear walking under it costs you your exams, so decide for yourself. The Old Library is the anchor: book ahead for the Book of Kells, but climb to the Long Room, a barrel-vaulted run of two hundred thousand books that hushes everyone who enters. Round the back, the squares turn modern — the Berkeley Library and Pomodoro's cracked golden sphere.
Back out the front, the curved colonnade across College Green is the old Irish Parliament, now a bank, with its House of Lords chamber intact. From there Dame Street runs you west toward the castle and the medieval city, or the Luas at Trinity takes you anywhere else.