Transepts
A transept was part of a medieval Christian church. Most churches were shaped like a cross, to remind people about Jesus' crucifixion, and the transept is the cross-piece of the cross.
Sometimes there were big rose windows (round windows) and doors in each end of the transept.
Here is a floor plan of Chartres Cathedral, looking down at the church as if you were floating over it. You can see the nave at the west end, the apse at the east end, and the transept between them.
To find out more about medieval churches and their transepts, check out these books from Amazon.com or from your library:
Arches to Zigzags: An Architecture ABC, by Michael J. Crosbie (2000). Shows what an arch is, or a gable, or an eave. For younger kids.
Eyewitness: Building, by Philip Wilkinson, Dave King, and Geoff Dann (2000). Lavishly illustrated, like other Eyewitness books for kids, and with good explanations of most architectural terms.
City: A Story of Roman Planning and Construction, by David Macaulay (1983).
