Walking around the entire downtown Houston area for about the past 5 months, I suspected underground garages connected to buildings due to the building sizes, the lights on there and with so few people walking on the streets. Even though it was near the end of the pandemic something seemed amiss. I never imagined that there were so many interconnected tunnels, skywalks, entrances, streets, garages, buildings, offices, shops and patios. One person stated that it was six miles in total length! I thought only people who work in these buildings could enter. On impulse I stepped into one of the numerous entrances; few are clearly marked. The entire system is kept immaculately clean. On a stormy/windy/hot/sunny episodic day, it can be a life saver. It can also be an incident avoider. During office opening/closing/lunch hours it feels like a human bee hive. My blood pressure shot up. At times other than office business hours, it is deserted. Then it felt scary. Most of the shops open late and close very early. They appeared to serve one and all. Eateries may only be open two or three hours for breakfast or lunch. Upon an item purchase some eateries provide a code or key for restroom use. Some ring up a purchase then inform you they only accept cards. With so many cameras, computers, security personnel, workers and people, I suspect they evaluate one and all. (see photos) There are three marked entrances to the tunnels in the one square block of McKinney-Main-Travis-Lamar. Stairs and elevators to the tunnels reach maps and retail store lists. It might not be a good idea to explore without reason. (more assorted photos)