The "Wahaca" you write, is actually how the name "Oaxaca" is pronounced. Oaxaca is a state in the southern half of Mexico.
Wahaka is a municipality located in the state of Oaxaca, Mexico. It is known for its rich cultural heritage, traditional artisan crafts, and mezcal production.
from wahaka
The city name is spelled Oaxaca, and no it is not the richest city in terms of GDP. Mexico City, the 8th wealthiest city in the world, is the wealthiest city in Mexico. To give that some perspective the wealthiest city in the US is New York City. New York City and Mexico City have nearly identical metro area populations (approx. 22 Million) yet New York's GDP wealth is nearly 3.5 times that of Mexico City and Nearly 3 times the wealth of the 6th wealthiest city, Paris. Tokyo is the worlds wealthiest city.