Sin City: It makes sense that the place known as Sin City would be one of the best places to hide for Hydra. But close on their heels are SHIELD, who also have a base on the strip. With locals and tourists running amok on the streets, there is potential for anything to happen. From a little gambling to an outright war.
Modern splendour: One of the newest hotels on the strip, the Cosmopolitan's overriding theme seems to be luxury and excess. It makes sense, then, that Hydra would be behind its construction and financing, unbeknownst to the majority of the hotel's guests. This hotel is the main base for Hydra.
