An island with several histories

If you can do it, blow a week’s pay at Wentworth by the Sea Resort Hotel and Spa (588 Wentworth Road, www.wentworth.com, 603-422-7322; rates start at $329). The only hotel in New Castle, it came close to demolition before being renovated and reopened seven years ago as a Marriott affiliate. From its white, battleship-size exterior to the phones in the guest bathrooms, the place demonstrates opulence. For those on a budget, next-door Portsmouth, the New Hampshire seacoast’s major city, offers chain hotels and quaint bed-and-breakfasts just a few miles away. The Comfort Inn (1190 Lafayette Road, www.comfortinn.com, 603-433-3338, rates start at $179) is an hour from Boston and sits near Interstate 95 and Portsmouth’s airport.

The Wentworth offers several dining options open to guests and to the general public. The Wentworth Dining Room (entrees start at $25) has the only piece from the original 1874 hotel, a mural of angels adorning the ceiling dome, as well as nice ocean views and a menu ranging from surf to turf. Latitudes Restaurant (entrees starting at $22; burgers, sandwiches, and small plates available) overlooks the hotel marina from a separate building and features indoor and deck dining and deliciously curious main courses (goat cheese wrapped in eggplant with greens and tomatoes, for example). It’s closed after mid-October until next May. Both restaurants are open for lunch and dinner, and the dining room also serves breakfast. Henry’s Market (52 Main St., 603-430-2008, sandwiches start at $3.25; soup-and-sandwich combos start at $6.75) is a general store that serves tasty luncheon sandwiches, panini, and soups in a cozy setting, with four tables inside and two outside. We recommend the Kitchen Sink: hummus, avocado, roasted peppers, and tomatoes on rye. Since you’re on the coast, you might want to scoot over to another neighboring town, Rye, for a classic roadside seafood meal. The Ice House (112 Wentworth Road, 603-431-3086, www.theicehouserestaurant.com, entrees start at $11.25) offers burgers, sandwiches, and chili along with the shrimp, clams, calamari, and haddock on the menu.

This is where you can have fun and save money. New Castle’s pivotal position overlooking both a river and the Atlantic Ocean made it a natural defense point, and the Fort Constitution Historic Site (Route 1B at the US Coast Guard Station, 603-436-1552) affords a self-guided walking tour through the ruins of this 1808 outpost, first used during the War of 1812. Also at the site, Portsmouth Harbor Lighthouse (adults $4, children age 12 and under $2), just repainted, has Sunday open houses from 1 to 5 p.m. through mid-October, during which you can climb its 48-foot tower for a view enjoyed since the lighthouse was built in 1878. The beacon can be seen 12 miles out to sea, and the place supposedly is haunted (the Syfy channel featured it). If vertical walks are what you prefer, then Great Island Common (adults 17-65 $3, children 6-16 $1, 5 and under free) offers plenty. Thirty-two acres of seafront green space and beach, it’s open 365 days a year, except to pets, banned from May 15 to Sept. 15. There are grill stanchions, picnic benches, and a playground.

Homebodies staying at the Wentworth can take a dip in the indoor pool, which is open until 11 p.m., or sip and sup in Roosevelt’s Lounge, named in honor of President Theodore Roosevelt, who in 1905 brokered the Treaty of Portsmouth (delegates stayed at the Wentworth), an agreement that ended the Russo-Japanese War and earned him the Nobel Prize for Peace. Also open until 11, the lounge serves salads and sandwiches (each starting at $9), light dinner (starting at $18) and drinks. But why be a landlubber? Portsmouth Harbor Cruises (64 Ceres St., Portsmouth, www.portsmouthharbor.com/cruises, 800-776-0915) offers one-hour evening cruises and 1 1/2-hour city-lights-cum-sunset trips, “lightly narrated’’ while you sip your cocktail. Should weather or your own tastes suggest the indoors, there’s the Music Hall (28 Chestnut St., Portsmouth, www.themusichall.org, 603-436-2400), offering concerts, films, plays, dance, and book events. Late summer and fall offerings include appearances by Canadian writer Margaret Atwood, historian Joseph Ellis, Art Garfunkel, and Grammy-winning trumpeter Chris Botti. The hall’s Founders Lobby Lounge serves coffee, cocktails, and cake Thursdays through Saturdays from 5:30 p.m. till midnight.