Lonely Planet review
To protect the harbour at night in times of war, an enormous chain was raised between the two 14th-century stone towers at the harbour entrance to La Rochelle, giving rise to the name Tour de la Chaîne (Chain Tower). There are superb views from the top and a whizz-bang new permanent exhibit about the Canadian voyagers.
Across the harbour it's also possible to climb the 36m-high, pentagonal Tour St-Nicolas .
The conical 15th-century Tour de la Lanterne , so named because of its role as the harbour's lighthouse (lit by an enormous candle), and one of the oldest of its kind in the world, is also referred to as Tour des Quatre Sergents in memory of four local sergeants, two of whom were held here for plotting to overthrow the newly reinstated monarchy before their execution in Paris in 1822. The English-language graffiti on the walls was carved by English privateers held here during the 18th century.
The gateway to the old city, Tour de la Grosse Horloge is a steadfast Gothic-style clock tower, with a 12th-century base and an 18th-century top. For safety reasons, it's not possible to enter.