The Town Hall is one of the buildings granted when you first get your city. No other building can be upgraded to a higher level than the Town Hall and the Town Hall cannot be upgraded higher than the character's level. In addition, each level of Town Hall increases your hourly gold production by 80.
(See the Building page for upgrade costs and cooldowns)
Starting at level 14, you can "levy" gold from your Town Hall 5 times per day with no cooldown. The gold gained by levying is equal to six times your city gold production (Town Hall hourly gold production plus Gold Refinery hourly gold production plus Academy hourly gold production plus Guild Tower Bonus).
The Town Hall displays a list of your current Gold Mines along with their location, production rate, and remaining time it will be in your possession. Each gold mine also has a View button and a Remove button (X), which provides a quick way to find the gold mine or simply abandon it.