Encore Boston Harbor is only three months away from opening and as of this week, you can now book one of the luxurious rooms at the $2.6 billion casino resort.

Encore’s online reservation system shows “opening night” rooms available beginning Sunday, June 23. Rates start at $777 for a night and you get a sizable room for that price. Additional nights could land you a lower rate, a Encore spokesperson said. Encore boasts that its premier king room, at 650 square feet, is the largest standard hotel room in New England. And that’s the standard room. From there, reservation options climb from premier harbor view rooms and signature suites to the 1,350-square-foot signature harbor view suites.

Also available are two-bedroom 3,350-square-foot residences and two limited-availability villas that total 5,800 square feet a piece. You won’t find the residences on the online reservation system just yet, however. To book those you’ll need to call reservations directly.

“From the furniture to the carpets and drapes, every guest room detail is custom, bespoke and unique, created exclusively for Encore Boston Harbor," said Robert DeSalvio, president of Encore Boston Harbor. "If guests want to relive this experience, they’ll have to come back.”

There are 671 guest rooms and suites and reservations can be made at www.encorebostonharbor.com or by calling reservations at 857-770-7100.

According to Encore, rooms include exclusive Wynn Dream Beds with 507-thread-count linens. Tech-friendly conveniences including flat-screen 4K ultra-high-definition televisions, high-speed Wi-Fi, bedside mobile charging devices, and a wireless iPad for one-touch access to room controls, resort information and guest services. A voice-activation system controls curtains, lighting, heating and air-conditioning, and privacy settings.

Bathrooms feature separate showers and deep-soaking tubs, dual sinks, marble floors, seated vanity areas with lighted mirrors, and flat-screen, high-definition televisions.

Encore sits along the Mystic River in Everett and in addition to the casino will feature an ultra-premium spa, retail, ballroom and meeting space as well as 15 dining and lounge venues.