Columbus was told by natives of the other ocean, and he sailed to the point where Balboa would start from when he discovered the Pacific. It's true that the Spanish never made much use of Balboa's discovery, perhaps because Balboa was very out of favor. But physically it wouldn't have been too difficult for the Spanish, having decimated the local natives, to create roads connecting the coasts and put ports on each side. It would have been easier and faster and safer than going around Cape Horn.

The point is that if Columbus really wanted to achieve his dream, discovering the Pacific would have been a major leap for him. It would have also made his reputation even more glorious(within his culture, it's well known that he was a jerk). But he stopped with the discovery close within his grasp and he failed to sieze it.

It's really a reminder to myself to not give up.