As global populations surge and people flock to live in cities, floor-space will increasingly become a resource which, quite literally, is thin on the ground. It's a problem that metropolises like New York faced, and solved, many decades ago - when space is limited, build up, not out.

But living amongst skyscrapers doesn't have to mean never seeing the sky. Rooftop bars which merge class and sophistication with a thrilling and novel sense of space can offer guests a truly memorable night out, without requiring any further land acquisition on behalf of the hotel owners. Hoteliers with the means to can provide guests with a truly unique experience without ever having to leave the hotel, all by capitalising on unused rooftop space.

To provide you with some inspiration, here are 10 of the world's best rooftop bars. They've been selected to showcase the huge variety of experiences that a hotel rooftop bar can provide - open-air or glass-and-steel, luxurious or down-to-earth, sublime or ridiculous. Some are small, modest affairs, and others are - well, less modest. But it all goes to show that, with a rooftop bar, anything is possible.

Glenmore Hotel Rooftop Bar, 3rd floor
Sydney, Australia

Built in 1921 and boasting panoramic views of the harbour, the Glenmore Hotel is a Sydney classic. The three-level establishment was renovated in 2012, and rooftop patrons can enjoy foods like salt & pepper squid, poke bowls, and black Angus sirloin. The Glenmore has an extensive beer menu and plenty of cocktails, and its retractable roof means that views of the Opera House and skyline can be enjoyed all year round.

The Silo Rooftop Bar, 11th floor
Cape Town, South Africa

Perched on top of the five-star Silo Hotel on Cape Town's waterfront, the Silo Rooftop Bar offers guests a frankly unbeatable view of the city's iconic Table Mountain, which guests can enjoy whilst bathing in the stunning infinity pool. After a dip, they can mull over an uninterrupted view of the South Atlantic from the bar, all while enjoying fresh oysters, pulled pork sandwiches, and plenty of cocktails or South African wines.

The Culpeper Rooftop Bar, 4th floor

The Culpeper is proof that you don't need a skyscraper to host a world-class rooftop bar. Head to the roof of this modest four-storey hotel and pub - which hosts just five guest bedrooms - and you'll stumble upon a rustic garden full of greenery in the heart of the city's Whitechapel financial district. London's relatively uncluttered skyline means that diners at the Culpeper don't feel hemmed in by endless skyscrapers, instead being able to enjoy their cucumber-themed cocktails whilst gazing out at the expansive city. They can shelter from inclement weather in the Culpeper's greenhouse-style indoor seating area.

The Bar Casa Gangotena, 4th floor
Quito, Ecuador

Located in the centre of the best-preserved historical Old Town in Latin America, Casa Gangotena's modest, plant-filled terrace boasts picturesque views of Ecuador's capital city, including the stunning Basicila Church. For a true taste of Quito, national brands like Espiritu de Ecuador, Cana Manabita, and the quadruple-distilled Amaranto gin are given pride of place at the bar.

Rooftop at QT, 
11th floor

Combining an indoor lounge and an open-air terrace, the Rooftop at QT offers classic and curated cocktails, along with a selection of bar meals like a Japanese Wagyu sandwich or pulled pork burger. It has a dress code to maintain its atmosphere of class and sophistication.

In a bid to maximise the utility of its outdoor rooftop space, QT also hosts morning yoga classes on the terrace. (Guests attending the hotel's 'Yoga In The Sky' class need not don a tux.)

Sky Bar at Grand Central Hotel, 8th floor

Boasting one of the world's most jaw-dropping infinity pools, patrons of the Sky Bar at Grand Central Hotel Barcelona get a virtually uninterrupted view of the entirety of Barcelona. The five-star hotel keeps the space exclusive to guests during the summer before 8 pm, when it opens up to non-guests to enjoy the Spanish dishes and cocktails.

CÈ LA VI at Marina Bay Sands, 57th floor

CÈ LA VI is a rooftop bar from the future. Located atop Singapore's iconic Marina Bay Sands integrated resort, the bar hosts one of the world's largest infinity pools. Guests can enjoy a cocktail and modern Asian cuisine with breathtaking views of Singapore, 200 metres above sea level.

Ozone Bar at The Ritz-Carlton, 118th floor
Hong Kong

The world's highest rooftop bar, Ozone at the Ritz Carlton serves drinks at 480 metres. Stunning vistas across Hong Kong and its surroundings can be enjoyed from within Ozone's futuristic interior or its lounge-like open-roofed terrace. The picture-perfect views are framed by large windows, and guests can sip on cocktails and champagne whilst dining on Brazilian and Asian tapas.

Salon de Ning at Peninsula, 23rd floor
New York City

No list of rooftop bars would be complete without mentioning New York City, the birthplace of the format. In a city squeezed for space, Salon de Ning at the iconic Peninsula Hotel offers a slice of tranquil luxury. Patrons can enjoy classic Asian décor by candlelight in the evening, with views of 5th Avenue and the surrounding skyscrapers of midtown Manhattan. There are plentyof house-cocktails to choose from, like the 'Ning Sling' - made with Hendrick's Gin, lychee, and passion fruit puree.

HI-SO, 16th floor

You don't need to go abroad to get a taste of what a rooftop bar can offer your customers. In the heart of Auckland's CBD, SO/ Hotels' rooftop bar HI-SO makes excellent use of the hotel's waterfront locations, with stunning views of Rangitoto Island and Waitemata Harbour. The hip decor is in keeping with the hotel's idiosyncratic style, and has proved a hit with the socialities of New Zealand's most populous city.