Agile practitioners equate having architectural plans with big-up-front-design. Nothing could be further from the truth.

Hawthorne Bridge, Portland, Oregon

If you fail to plan, you plan to fail.

Scott Hurlbert provides an excellent analogy to describe the optimal amount of planning for software projects.

The Agile Planning False Equivalency

There is so much more to learn by reading Righting Software by Juval Löwy, or by visiting the IDesign website.