An extraordinary opportunity to create a new landmark estate on Round Hill Rd's premier building site: a nearly 20-acre offering at a 560 ft elevation - one of the highest points on Round Hill with a spectacular 7,000+ sq. ft. guest house for immediate liveability during the construction phase. Potential to build notable 22,000+ sq. ft. main house with optimal south-facing orientation and Long Island Sound views from second floor on 8-acre lot and additional 12,000+ sq. ft. on 4.2 acre lot for a total of 35,000+/- sq. ft. The existing stone guest house built in 2015 was designed by acclaimed architect Christopher Pagliaro with interior design by Arthur Dunnam of Dunnam Zerbini Design and offers south-facing pool with spa, studio apartment with 6th bedroom and attached 3-car garage. Additional buffer lot of 2.3 conservation acres. DISCLAIMER: Photos labeled CONCEPTUAL RENDERING are for illustrative purposes only. Home design shown is not an approved or proposed architectural plan and is intended solely to illustrate the potential use of the property. Buyer to verify all zoning, building, and site requirements.