Sky Garden

Sky Garden crowns the top three floors of 20 Fenchurch Street, a curved glass tower designed by the Uruguayan-American architect Rafael Viñoly and completed in 2014. Its outward-leaning profile, widening as it rises rather than tapering like most skyscrapers, quickly earned it a nickname London takes to easily: "the Walkie-Talkie."

Rather than keeping its best floors for private offices, the tower opens its summit to the public as London's highest public garden — and, unlike most of the city's viewpoints, one that costs nothing to visit. Terraces of Mediterranean and South African planting spill across three levels beneath a great glazed vault, with open-air balconies on either side framing panoramas that take in Tower Bridge, the Shard and the dome of St Paul's.

Before it became known for its garden, the tower briefly made headlines for something else entirely. During construction in 2013, its curved, highly reflective glass facade concentrated sunlight into a beam intense enough to melt part of a parked car on the street below — earning the building a less flattering nickname, "the Walkie-Scorchie," until permanent external sunshades were fitted to fix the problem for good.

Despite being free, Sky Garden isn't a walk-in attraction: demand quickly overwhelmed early open-door access, so entry now runs entirely on advance timed tickets booked online, a policy that keeps the gardens pleasant rather than overcrowded.

Because tickets are free, they're released on a rolling basis and go quickly, particularly for weekend and sunset slots — booking well ahead online is the only reliable way in, since turning up without a reservation rarely works. Slots can open up a few weeks out, so it's worth checking back if your first-choice time is unavailable.

Bars and restaurants occupy the garden levels for anyone who fancies a drink with the view rather than just a quick look, and the terraces stay open to anyone holding a booking regardless of the time slot's original purpose. For a city where paid-for towers like the Shard and the London Eye charge steeply for a view, Sky Garden remains one of the best-value ways to see London from above.