Rare opportunity in Mastic Beach. Fully renovated Cape on a private 1+ acre corner lot with river views, modern upgrades throughout, and flexible living space including a possible 4th bedroom or office. Welcome to 4 Riverside Avenue, a beautifully updated home that offers the perfect combination of space, privacy, and modern comfort. This property stands out with its oversized lot, thoughtful renovation, and peaceful natural surroundings. The home features 3 spacious bedrooms, a potential 4th bedroom or office space, and 3 full bathrooms, providing flexibility for today's lifestyle. Natural light fills the home, highlighting the neutral color palette and hardwood floors throughout, creating a warm and inviting atmosphere from the moment you enter. The fully renovated kitchen is designed for both everyday living and entertaining, featuring brand new stainless steel appliances, granite countertops, and custom cabinetry. The bathrooms have been updated with modern tile finishes, adding a fresh and clean design throughout the home. Major upgrades include a new roof (2026), new electric, new fencing, and updated landscaping. The elegant Mountain Black metal roof adds both durability and striking curb appeal. The spacious basement with walkout access provides excellent potential for additional living space. With areas ideal for a bar, cinema room, recreation space, or future finishing, the lower level offers incredible versatility. Outside, the property truly shines. Sitting on over an acre of land, the home features new trees, fresh landscaping, a fenced front yard, and a fenced backyard, creating a peaceful outdoor setting with plenty of room to relax, entertain, or expand. This home offers convenient access to nearby parks, waterfront areas, shopping, and local amenities. If you are looking for a fully renovated, move in ready home with space, privacy, and modern upgrades on a rare oversized lot with river views, this is one you will want to see in person.