Complex sentence: The EverLine Rapid Transit System is an ART line is being built in Yongin, connecting the city and the Everland Theme Park with an extension of the Seoul Subway now under construction.
Split into simpler sentences: The EverLine Rapid Transit System is an ART line, currently being built in Yongin. The line will connect the city to the Everland theme park, with an extension of the Seoul Subway now under construction.