This is a flat in the big tower at Gunwharf Quays in Portsmouth, the one they call the Lipstick building. It's on one of the upper floors, so you get a good view out over the harbour and the coast. It's an apartment, so everything is on one level.
It sleeps four. Two bedrooms, and each has its own bathroom. It's got a 4 Star rating, which means it's well-equipped and comfortable. The building is modern, so the stairs in the common parts are fine, but you'll be using a lift to get up to the flat.
You're right in the middle of Gunwharf Quays. There are shops, a cinema, restaurants, and pubs literally on the doorstep. The flat is quiet, but step outside and it's busy. The Harbour train station is a five-minute walk away. You can be in London in about an hour and twenty minutes.
For history, the Portsmouth Historic Dockyard is a fifteen-minute walk. You can see HMS Victory and the Mary Rose there. Southsea seafront and the common are about two miles away if you want a proper walk by the sea.
Facilities: it's got a washing machine, a dishwasher, WiFi, and a TV. Bedding and towels are included. There's a cot if you need one, and secure bike storage. You get a parking space. No pets.
Useful links: Visit Portsmouth and National Trust Hampshire & Isle of Wight for ideas if you're planning to explore further.