Simplify the following text for a Grade 12 native English-speaking person.
Original: One such example was constructed in the 9th century by Muslim geographers and cartographers working under the Abbasid caliph , Al-Ma ` mun .
Simplified: One such example was made in the 9th century by Muslim geographers and cartographers working under the Abbasid caliph , Al-Ma ` mun .