Why are there windows on the engineer castle?

The 16 Windows on the engineer castle are symbolic of the 16 core principles of engineering. These principles, outlined by the National Academy of Engineering, are the basis for engineering ethics, and they are:

1. public welfare and safety
2. health, welfare, and safety of the public
3. advancement of the state of engineering knowledge
4. protection of the environment
5. enhancement of the quality of life
6. international cooperation
7. respect for human dignity
8. responsibility to society
9. loyalty to employers
10. fairness to colleagues
11. integrity in practice
12. objectivity in decision-making
13. avoidance of conflicts of interest
14. openness in communication
15. respect for intellectual property
16. professional development

The 16 window configuration of the engineer castle is a visual representation of these principles, and serves as a reminder of the ethical standards to which engineers should adhere.