I discovered Hotel Gillow by default after not being able to get a booking at Hotel Catedral. It's clean, the location is excellent and the front desk staff, friendly. The rooms at the Gillow are much improved after the remodeling of the floors (the old carpet was removed and new wood-like flooring installed). Although the Gillow doesn't have the services of Hotel Catedral, (hence one less star) it's the perfect place to stay for a night or two, if one prefers a downtown layover point before or after a flight. It's cheaper than the airport hotels, even with the taxi fare and what could be more fun than staying steps from the zocalo? If you're sensitive to noise (hey, it's a big city), bring ear plugs.
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