Conclusion
It seems that the Lagunilla flea market will never end, even with the growth of Mexico City, as it is already part of the tradition of this city, as well as of that inherited custom of doing business that Mexican have in their blood.
Last but not least, the Lagunilla flea market is a place where, in one way or another, people sympathize as Mexicans and foreigners, regardless of their status as everyone goes to La Lagunilla either by necessity or eccentricity.
How to get there: La Lagunilla flea market is very accessible by subway lines 8 (Garibaldi station) and B (Lagunilla station).
Useful apps to navigate in Mexico City: Metro DF (for iOS and Android), Metro y Metrobus de Mexico (for iOS and Android).