Simplify the following text for a Grade 9 native English-speaking person.
Original: Prior to the designation of the boundaries of the National Park , the term `` Snowdonia '' was generally used to refer to a much smaller area , namely the upland area of northern Gwynedd centred on the Snowdon massif , whereas the national park covers an area more than twice that size extending far to the south into Meirionnydd .
Simplified: Before the National Park was made , `` Snowdonia '' used to refer to a much smaller area around Snowdon itself .