The Promenade de la Treille runs along the southern wall of the old town, the highest walkable point in Geneva, lined on one side with chestnut trees and on the other with a continuous wooden bench claimed to be the longest in the world at 126 metres. The promenade was created from the old city ramparts in the 18th century as a place for the patricians of Geneva to take the air; the view across the lower town and out to the Salève and the French Alps is one of the city's classic vistas.
At the eastern end stands the marronnier officiel, the city's official chestnut tree — every year an inspector waits for the first leaf to unfold and writes the date in a register that goes back to 1818, the longest continuous phenological record in Europe. The promenade is at its best in early evening, when the late sun catches the lake and the Alps glow pink. The walk takes ten minutes from end to end and connects to the Parc des Bastions at one end and the Esplanade Saint-Antoine at the other.