ancient city; former capital
Refers to a city that was once a capital or has a long historical significance, often used for places like Kyoto or Nara.
京都は日本の古都として知られている。
Kyoto is known as an ancient capital of Japan.
During summer vacation, I visited an ancient city with my family.
古都の街並みを散策するのが好きだ。
I like strolling through the streets of the old capital.
Kyoto is known worldwide as an ancient capital.
都 is a general word for 'capital' or 'metropolis' with no historical implication, whereas 古都 specifically means a city that was once a capital and retains a sense of history.
Compound of 古 (old, ancient) and 都 (capital, city). The reading こと is the standard on'yomi combination.