Also called the Coulée Verte René-Dumont or just Coulée Verte, this is a nature trail running along the top of an abandoned railway line. A stroll along this 4.7-km-long elevated walkway is a fabulous way to take in Paris from another angle while enjoying the nature vibe of this urban green space. This sounds a lot like New York's High Line, you may think – but Paris was the first city to open this linear park on an elevated viaduct back in 1993.

It's a very pleasant 90-minute stroll from one end to the next. Along the way, you'll pass flower gardens, bamboo groves, trellises of climbing plants, rose bushes, and lime and hazelnut trees, while catching glimpses of the Parisian skyline and scenes of street life below. There are also plenty of benches, picnic spots and gardens offering a rest stop and a chance to soak up the nature vibe.

Accessed via stairways and lifts, this green walkway in the sky begins close to the Opera House at Place de la Bastille and stretches 4.7 kilometres eastwards to the Bois de Vincennes. Along Avenue Daumesnil, the archways of the 10-metre-high brick viaduct have been converted into high-end speciality shops. Dubbed the Viaduc des Arts, there's a shop tucked under each archway peddling artistic wares such as jewellery, design furniture, decorative porcelain and musical instruments.

Walk across the cable-stayed footbridge to get to the Jardin de Reuilly, a popular city park with picnickers and sunbathers. Heading further east, the trail slices through a contemporary building specially built to accommodate the walkway that has become a landmark. From here, the trail descends to street level and becomes a tree-lined cycle path running along Allée Vivaldi and accessible to cyclists and rollerbladers as well as walkers.

For a bird’s-eye view of Paris from 150 metres up in the sky, head to Parc André-Citroën in the 15th arrondissement. Tethered here is the Ballon Generali, a huge hot air balloon that happens to be the world's biggest and the third highest viewpoint in Paris. Once you're in the park, the balloon is easy to locate: just look up.

Take the 10-minute ride up in the sky for one of the best views of Paris. Once the balloon reaches its maximum height, you'll have sweeping views of the river Seine and the Eiffel Tower, and on clear days you can see the entire city and its surrounding suburbs.

The balloon is also used as an indicator of air pollution. It measures the concentration of particles in the air and changes colour according to the pollution level from green to yellow to red.

Just be aware that trips are cancelled during bad weather so check the website before heading out. Also, the number of passengers is limited to 30 so on busy days there may be a wait involved.

For an unforgettable meal with a view, climb to level two of the Eiffel Tower. Le Jules Verne has become an iconic restaurant in the sky, thanks to 'super chef' Alain Ducasse who ruled the kitchen here for ten years and earned it a Michelin star. With a new lease, the kitchen has now been taken over by Chef Frédéric Anton from the three-Michelin-star Le Pre Catalan in Bois du Boulogne. The restaurant is also getting a new look and undergoing a stylish renovation and is set to re-open with a splash in July.

Of course, lovers of contemporary French cuisine don't only come for the food but also for the stunning views of the City of Lights from 125 metres up. This is one of the city's top dining destinations so you'll have to reserve long in advance: at least one month for lunch and three months for dinner. The restaurant has its own private elevator accessible from the Le Jules Verne reception desk at the Eiffel Tower’s southern pillar.

Some of Paris' most intriguing attractions are actually under the bustle of the city's pavements. Head underground to the Paris Sewer Museum in the 7th arrondissement to learn all about the history of waste management in the French capital. The Paris sewer system covers an underground network of 2000 kilometres and is the world's biggest and the most modern. A 500-metre section of it is accessible to the public and can be explored on foot. Get insights into how the sewer system was built, how waste water is treated, and fascinating facts about water in Paris.

You could say that all your senses are engaged here. There's the sound of water flowing from active feeder sewers below you. You'll see the huge metal balls used to clean the sewers: propelled by water pressure, they move through the sewers and push out debris. You'll also see other pieces of maintenance equipment, staff uniforms, old photographs, and a lost and found of objects retrieved from the sewers, including an impressive collection of swords and weapons. As for the smell, expect a stink but it's really not as bad as you'd imagine. But if you have a sensitive nose, you may want to avoid a visit during the summer.

The Paris Sewer Museum is currently closed for renovation but will reopen in July 2020.

Another less-known subterranean attraction is the Paris Catacombes, located 20 metres and a flight of 131 steps underground. A 1.5-kilometre section of a network of tunnels once used as quarries is the final resting place for a collection of skeletons exhumed from overcrowded Parisian cemeteries at the end of the 18th and the beginning of the 19th centuries.

The bones of over six million people – three times the city's current population! – now lie here in this underground cemetery. The bones have been arranged in an intriguingly decorative way: stacked to create wide columns or long walls of bones laid in rows of tibiae alternating with lines of skulls.

Only 200 visitors are allowed inside at a time so be prepared for queues at the entrance.