From PathfinderWiki

The Castlegate is one of four gates that pierce the city wall of Magnimar sitting at the border between the Keystone and Lowcleft districts of the city. While Castlegate is not as large as the Twins' Gate in the Grand Arch district it is the busiest of all the city gates and is often the first sight that a land bound trader sees when he enters the city. The Castlegate is so busy that it is directly responsible for almost all of the hustle and bustle of The Marches.1