Plenty of those early huge capital cities got lost.
Angkor Wat, Edo, Vilcabamba, Troy, Helike, Ai, Aztlán, Ys, Shambhala, Xanadu, Carthago, Karakorum, Niniveh, Persepolis, Ur, Samarkand, ...<p>See e.g. <a href="https://en.wikipedia.org/wiki/Lost_city" rel="nofollow">https://en.wikipedia.org/wiki/Lost_city</a>