Simplify the following text for a Grade 6 native English-speaking person.
Original: It includes a swampy area along the Oder known as the Oderbruch , about 60 km in length and 17 km in width .
Simplified: Much of the district is mainly agricultural land , but there is a swampy area along the Oder called the Oderbruch . The Oderbruch is aabout 60 k in length and -RCB- in width .