Excellent choice for exploring historic downtown.
Holiday Inn Zocalo is located on the northwest corner of the Zócalo (Monte de Piedad and 5 de Mayo streets). The hotel is actually two buildings connected internally. The main building is a historic monument, with its interior completely improved. Its foundations were part of the palace of Moctezuma, and later of the residence of Hernan Cortez. Then it became the official house of the viceroy.
Our room (#214) is a corner room, with wonderful views to the Metropolitan Cathedral and the National Palace. The furniture and decoration were very refined Mexican. It had a walk-in closet, a vanity, a toilet in its own room, and a separate shower. It had a big plasma TV with cable service. The AC controls were on the wall, with registers near the ceiling, directed towards the living room (thank goodness, we really hate the window AC units). The floors were wooden, and the ceiling had big vigas.
Just be aware that, like the great majority of toilets anywhere in Mexico, you cannot throw toilet paper inside the toilet, because you will block it. You must use the trashcan located next to it. This happened to my 7-year-old daughter, and the toilet room was flooded in no time. The hotel's staff attended our cry for help immediately, and they fixed up the toilet and cleaned the whole mess right away and with good attitude.
The price of the room included a breakfast buffet, which was very Mexican and wonderful, with fresh tropical fruit, fresh juices, eggs made per your request, chilaquiles, beans, Mexican hot cholocate, cereals, etc. The restaurant is located on the covered roof of the hotel, so you can enjoy the wonderful views and weather.
The hallways are beautifully decorated with Mexican talavera ceramics and historic pictures and artifacts. We never made it to the exercise room, so I can't tell you how good is it. There is no pool.
The hotel's location is excellent for exploring historic downtown. Many wonderful places are located within walking distance, and the metro has a station right underneath the Zócalo. We felt very safe walking late at night in the Zócalo, because there is plenty of activity and policemen continuously patrolling by foot and car.
We found a great place to eat just a block west from the hotel (on 5 de Mayo street), called "Café Popular", which has been in service for over 60 years. It's open 24 hours, they make their own breads ans pastries, and their coffee is just wonderful. Just be aware that they only take Mexican cash, not dollars.
Also, there is a 24-hour 7-Eleven on the first floor of the hotel, facing the Zócalo, which is very convenient for quick errands.
About the noise... we had no problem (neither our 5 and 7-year-old children). Of course everyone is different. If you think you may be sensitive to the outdoor noises of a big city, bring with you earplugs, and you'll be OK.