I will be a retard and I will say orc's shelters(idk how is it called so i will name it by biggest building in the village), but if you ask me to answer nicely i would say that Silver cities are the best
I like Orcs Castle. Very well fit with their livestyles. Orcs are the most unique race in H5 without magic.
Inferno, Necropolis, Dungeon - I don't know why but dark races can be scary. Inferno with lots of flames and Roman like buildings is nice. Maybe Hell can look impresive as our planet. Dungeon place of mysteries and shadows. Impresive underground city and beauty girls like Ylaya or Witches. Necro as being home to undead is the place you don't be. Plenty units are often used in horror films. dark solid place. All 3 are unique and give us climat and culture of each race.