1. The Old City's four quarters — Old City, Jerusalem
Free to enter, endless to walk, and the reason everyone comes to Jerusalem.
All seven open gates are free, and so is everything inside that most visitors come for: the Muslim quarter souk, the Cardo, the Armenian and Christian quarters, the Via Dolorosa and the Church of the Holy Sepulchre.
The scale is deceptive — the whole walled city is under a square kilometre — but it takes days to stop finding new lanes, and a first pass should be slow and aimless.
The only genuine cost is being stopped by security at the gates, which is quick, and resisting the souk.
Good to know: Enter by Damascus Gate rather than Jaffa Gate at least once — it is the livelier arrival by far.