Mercury City. . . Is it in Sol? You know Mercury is 350+ Celsius during the day and -17 Celsius at night. . . with an orbit period of 88 days, mainly comprised of Iron (assumed from infrared scans) and happens to spin fast enough to see two sun rises, if I'm not mistaken it is about 2.5 rotations per Earth day. . . assuming a city would not melt. . . I would think that just the rotational force should destroy a city, probably even a ship attempting to enter orbit.