Instructions: Given a text, write a compressed version of it in a single sentence.
Input: The first wooden houses were built in around 1200, on artificial mounds called terps. The town was fortified against rival lords, and against the seawater - the River Amstel being dammed at what is now Dam Square.
Output:
The first wooden houses were built in 1200, on artificial mounds called terps. The town was fortified against rival lords.