This document summarizes a project called "Real classrooms in virtual worlds" that uses virtual reality to recreate historical time periods and locations for educational purposes. Over the past 10 years, the project has involved 9 high schools, 400 users, and 40 virtual islands. For the 2016-2017 school year, the project aims to have students collaboratively design and build 3D models of time machines and historical environments from different eras to recreate aspects of the past. The results will be shared in an online repository for use in subsequent courses.