Based on your query, I would recommend using ScratchJr to help your students build an online city. This tool is designed to introduce young learners to programming in a fun and engaging way.

The block-based coding system with icons makes it easy for students to understand and use. They can use these blocks to create their own interactive stories and games, which could include building an online city.

The shareable projects feature of ScratchJr also allows for collaborative learning experiences. Students can work together to build different parts of the city, promoting teamwork and problem-solving skills.

Moreover, ScratchJr is a free programming language available on multiple platforms, making it accessible for all students.

In summary, ScratchJr provides a fun, engaging, and educational platform for your students to build an online city while learning basic programming concepts.