The city that flew

you were told by your grandmother that there was an ancient city that was more advanced then the most advanced computers and as you grown up you told her tails but everyone thought you were weird and a nerd for believing in such things and became an outcast and so when you grew up you didn't lose hope you bought a medium sized sub and modified it with the best tech money can buy and your objective is to find the city and all its glory and prove those that didn't believe you and called you a nerd and no one calls you a nerd