Now look to your left. This is the Low Battery of San Diego (Bateria Baja de San Diego). Imagine being a 16th century invader and staring at the cannons protruding from the flared openings called embrasures. Equally daunting was another set of guns positioned above. If you have time, you can continue exploring the defensive wall in either direction. Heading south brings you to a bastion called Invincible Fort (Fuerte Invencible). This is across from the Don Diego cruise and ferry terminal.