Mexico City is home to many museums including the Anthropology Museum, The National Art Museum (MUNO) and the Frida Kalho Museum.
Mexico City is well-known for their cuisine. From street food to fancy restaurants the possibilities are endless. For tacos we loved Tacos Los Alexis and Tacos Atarantados have Uncle Leo's stamp of approval. If you're looking for some mezcal and mole be sure to check out Azul Historico or Azulisimo. Also stopping by Churros el Morro for a sweet treat is a must and they are scattered all over the city.
The Historic Center is a neat place to visit during the day. This was the Aztec's main center. When Hernan Cortez took over he destroyed their temples and built a cathedral in it's place. The Templo Mayor ruins lie next to cathedral. Today, this part of town is the center of Mexican government. September 16th is Mexican Independence Day so there will be festivities this weekend.
Chapultepec Castle is scenic and full of history. If you choose to check it out, wear some comfy shoes as it requires a hike up a hill.
Take a trip to see the pyramids if you are feeling adventurous. I would recommend hiring a driver. Also, there is a restaurant nearby, La Gruta, with delicious authentic food and it's located in a cave (reservations needed).