The closest is Marinid Walls of Algeciras, 1 km north-east of the city centre; the most famous is Moorish Castle — #792 of 8,133 worldwide — 10 km east. The oldest dated site in the circle is Roman Theatre of Cádiz, founded c. 50 BC.
The 100 km circle reaches into 3 countries — Spain (35), Gibraltar (2), Morocco (1).
