On the south end of Parque Central [1], the Palace of the Captains General dates to 1558 and was once the seat of government for the entire Central American territory from Chiapas [2] to Costa Rica [3], of which Antigua was the capital, until 1773.
Its imposing architecture is dominated by a row of 27 arches on both of its floors. It once housed colonial rulers, the royal mint, the judiciary, and tax offices, among other things. Today it houses the police department and Sacatepéquez departmental government headquarters.
Links:
[1] http://www.moon.com/destinations/guatemala/antigua/sights/parque-central
[2] http://www.moon.com/destinations/chiapas
[3] http://www.moon.com/destinations/costa-rica