Mexico City is built on a lake, or rather it was, and Xochimilco is the part of that old water world that survived. Before the Spanish, the Aztecs and their neighbours built chinampas, narrow artificial islands of mud and reeds held in place by willow trees, and farmed them intensively to feed Tenochtitlan. Canals ran between the plots, and the whole system was a remarkably productive kind of garden. A part of it still works, and it earned a place on UNESCO's World Heritage list in 1987. The name is Nahuatl and means roughly the place of flowers, which suits the nurseries that fill the district.
For most visitors the main attraction is a ride on a trajinera, a long, flat, brightly painted boat poled slowly along the canals, with mariachi bands, taco boats and flower sellers alongside. It is touristy and tremendous fun, particularly on a Sunday when local families pile in with huge picnics. Farther out, the canals are quieter, and on the deeper channels you can find the axolotl, the strange salamander that never grows up and is a symbol of the city. A famous and slightly eerie corner is the Island of the Dolls, where hundreds of weathered dolls hang from trees.
On a motorbike, this is Mexico City at its most demanding and its most rewarding. Traffic can be thick, speed bumps called topes appear without warning, and the ring roads are huge and fast. Motorcycles weave between lanes, and you need to keep your mirrors and your wits about you. The reward is that the south of the city, around Xochimilco and the Cuemanco canoeing track, is full of green and open spaces. Weekend mornings are the best times, before the crowds arrive.
Fuel is everywhere, and the market has superb food, from tamales to esquites, and the garden centres at Madre Selva are a joy even if you have nowhere to put a plant. At 2,240 metres, the city is high enough to make engines run a little lean, and the afternoon rain in summer arrives like clockwork.