Based on your search query, I recommend using Common Curriculum. This tool is designed to help teachers create and manage their lesson plans efficiently, which could be beneficial for your sustainable city project.

With Common Curriculum, you can create a detailed lesson plan for your sustainable city project. The tool's Digital Lesson Planning feature allows you to create individual lesson plans and wider curriculum maps for the term and year. This could be useful for planning out the different stages of your project, such as research, design, and presentation.

The Integration with Other Digital Systems feature allows you to pull in content from other tools, such as images, videos, links, or files from Dropbox or Google Drive. This could be useful for incorporating multimedia resources into your project.

The Standards Tracker feature can help you ensure that your project aligns with educational standards. This could be useful for ensuring that your project is academically rigorous and meets your educational goals.

Finally, the Class Websites feature allows you to create a class website where you can share your project with students and families. This could be useful for showcasing your students' work and keeping parents informed about what their children are learning.

Common Curriculum offers a free basic plan, making it a cost-effective solution for your needs.