Royal Observatory Greenwich

Deal with this first, because it decides whether the visit happens.

The observatory sits at the top of Greenwich Park and the climb from the riverside is a genuine ascent — steep, sustained, and hard work on a warm day. Visitors with mobility difficulties describe turning back partway.

It takes ten to fifteen minutes at a steady pace.

The alternatives: a bus runs up the hill, and a taxi can reach the observatory gates. Both remove the problem entirely and are worth using rather than abandoning the visit.

Coming down is easy and the route through the park is pleasant.

Wear proper shoes. The paths are paved on the main routes and uneven elsewhere.

The most useful thing to know before you buy a ticket.

The view from the hill — London laid out below with the naval college in the foreground, the Docklands towers across the river and the City beyond — is in the public park and costs nothing.

It is one of the finest panoramas in London and it is the thing most visitors photograph.

You can also see part of the meridian line marked outside the paid courtyard, from the gate, without entering.

So the honest position: if the view is what you came for, walk up, look, and spend nothing. If you want the clocks, the meridian courtyard and the astronomy, buy the ticket.

The reviews split almost exactly along that line.

Inside the paid area: the meridian courtyard with the line itself, Flamsteed House with the astronomers’ apartments, the Octagon Room, the time ball, and the collection of historic clocks.

The Harrison sea clocks are the centrepiece and are the reason the site matters — the instruments that solved the longitude problem and made accurate navigation possible. They still run.

The Great Equatorial Telescope sits under its onion dome.

Also included: an audio guide, which is well regarded, and access to the astronomy galleries.

One recurring complaint: parts of the site have been closed for refurbishment for extended periods, including the planetarium at times, and visitors who paid full price for a partly closed site felt short-changed. Check what is currently open before buying.

The reason most people come, and it is worth knowing what to expect.

A metal strip set into the courtyard marks zero degrees longitude, with the hemispheres either side. Standing with a foot in each is the photograph everybody takes.

There is a queue for it at busy times, and it moves slowly because everyone wants the same shot.

A laser projects the line north across London after dark on clear nights, which is free to see from the park.

One curiosity worth mentioning: satellite navigation places the actual prime meridian a short distance east of the line, because the definition shifted with modern measurement. The line you photograph is the historic one, and the discrepancy is itself a good story.

Go early or late to avoid the queue.

A separate ticketed show in a dome beside the main observatory, running several presentations daily on planets, stars and space exploration.

Opinion divides sharply. Some visitors rate it the best part of the day, particularly with children. Others describe it as short and slight for the price, and a few expected a larger facility than it is.

Shows are timed and booked separately or as an add-on.

It has been closed for refurbishment at points, which has caught out visitors who bought tickets expecting it to be included.

Check it is open and running the show you want before building the visit around it.

This is the most divided set of reviews of any Greenwich attraction, and both positions are reasonable.

Against: the paid area is compact, the meridian line is a metal strip with a queue, parts have been closed for refurbishment, and the view — the thing most people actually want — is free outside the gates.

For: the Harrison clocks are genuinely significant objects, the audio guide is good, the astronomy content is well presented, and standing in the room where the world’s time was standardised is not nothing.

The deciding question is whether you care about the horology and the history of navigation. If you do, the ticket is fine. If you came for a photograph and a view, save the money and enjoy the hill.

Combination tickets with the Cutty Sark improve the value if you are doing both.

An hour to ninety minutes inside the ticketed area with the audio guide.

Add half an hour for the planetarium show if you take one.

Add the climb, fifteen minutes each way, and time at the top for the view.

So two hours covers it comfortably.

As part of a Greenwich day it is the afternoon element, with the free museums at the bottom of the hill filling the morning.

The site closes in the late afternoon, earlier in winter, so leaving the hill until last risks arriving after it has shut.

August is the busiest month by a clear margin, with July and September close behind — a summer pattern driven by the park as much as the observatory.

November, February and January are the quietest.

Within the day, first thing gives you the meridian courtyard without a queue.

Late afternoon gives the best light for the view over London, with the sun behind you on the city.

On a cold clear winter day the visibility from the hill is the best of the year and the site is nearly empty.

Check the closing time for your date; it moves substantially between seasons.

Works well, and the meridian line is the hook.

Standing with one foot in each hemisphere is a concrete idea that children grasp immediately, and the photograph is the souvenir.

The astronomy galleries are interactive and pitched at families.

The planetarium is the part that lands hardest with children, when it is running.

The time ball dropping on the hour is a small event worth timing for.

The climb is the obstacle with small legs — the park at the top gives them space to recover, and the run back down is its own reward.

The site itself has reasonable provision, with step-free routes into most of the buildings and accessible toilets, but the approach is the problem.

The walk up through the park is steep and there is no easy step-free route on foot.

A bus runs up the hill and taxis can reach the gates, which is the practical solution and is worth planning rather than attempting the climb.

Within the site, Flamsteed House has some level changes and original stairs.

A free companion ticket is generally available for visitors with disabilities.

The view from the hill, which is the free part, is reachable by the same bus or taxi.

Reach Greenwich first — by DLR to Cutty Sark, by river boat to Greenwich Pier, or by rail to Greenwich station — then climb the hill through the park, which takes ten to fifteen minutes from the riverside.

The park entrances are signposted and the path up is obvious.

Buses run up the hill from the town centre for anyone who would rather not walk.

The National Maritime Museum, the Queen’s House and the Cutty Sark are all at the bottom of the hill and are the natural other half of the day.

Blackheath, on the far side of the park, is a pleasant walk out if you want to leave the other way.

The reviews here divide more sharply than anywhere else in Greenwich, and the split is entirely about what people wanted.

The disappointing version: climb the hill in August heat, queue for a photograph on a metal strip, find the planetarium closed for refurbishment, walk round a small site in forty minutes, and conclude it was expensive for a line on the ground.

The good version: check what is open before booking, come early or late, take the audio guide, spend proper time with the Harrison clocks and the story of longitude, watch the time ball drop, and come out onto the hill for the view over London.

And if the horology does not appeal: the view is free, the park is free, and nobody will stop you enjoying both.