After visiting some of the landmarks just inside of the San Juan Gate, continue your leisurely stroll along Paseo del Morro. The walkway extends to Castillo San Felipe del Morro San Juan, the number one attraction in Old San Juan. Along the way you can continue to admire the features of the impressive city walls. This is Bastión de San Agustín. The outward projection of the curtain wall allowed soldiers to defend the flanks with heavy artillery during an attack from the sea.