Istanbul for one day- must see

If you are doing a stopover via IST airport, make sure you allow plenty of time to/from airport, at least one hour to get to historic area from airport and you need to allow 3-4 hours to return to airport and get back through airport to onward flight. The 24 hours becomes quickly less time with all of that, plus sleeping. You could start with any of these, courtesy of the forum host https://www.ricksteves.com/europe/turkey/istanbul.

▲▲▲ Hagia Sophia Constantinople's Great Church, later converted to an Ottoman mosque.

▲▲▲ Blue Mosque Ahmet I's response to Hagia Sophia, named for its brightly colored tiles.

▲▲▲ Topkapı Palace Storied residence of the sultans, with endless museum exhibits, astonishing artifacts, and the famous Harem.

▲▲▲ Grand Bazaar World's oldest shopping mall, with more than 4,000 playfully pushy merchants.

▲▲▲ Mosque of Süleyman the Magnificent The architect Sinan's 16th-century masterpiece, known for its serene interior and the tombs of Süleyman and his wife, Roxelana.

▲▲▲ Bosphorus Cruise Public ferry ride on the Bosphorus Strait, offering a glimpse of untouristy Istanbul (and an Asian adventure).

▲▲▲ İstiklal Street Cosmopolitan pedestrian-only street in the New District, teeming with shops, eateries, and people.

▲▲ Basilica Cistern Vast sixth-century subterranean water reservoir built with recycled Roman columns.

▲▲ Turkish and Islamic Arts Museum Carpets, calligraphy, ceramics, and other traditional arts on display at the former İbrahim Paşa Palace.

▲▲ Istanbul Archaeological Museums Complex covering Istanbul's ancient civilizations, including sumptuous tiles and highly decorated sarcophagi.

▲▲ Spice Market Fragrant and colorful spices, dried fruit, and roasted nuts inside a 350-year-old market hall.

▲▲ Galata Bridge Restaurant-lined bridge spanning the Golden Horn, bristling with fishermen's poles and offering sweeping views of the Old Town and New District.

▲▲ Chora Church Modest church outside the Old Town with some of the best Byzantine mosaics in captivity.

▲▲ Galata Tower 14th-century stone Genoese tower with the city's best views.

▲ Hippodrome Roman chariot racetrack-turned-square, linking Hagia Sophia and the Blue Mosque.

▲ Gülhane Park Former imperial rose garden, now a grassy park.

▲ Rüstem Paşa Mosque Small 16th-century mosque of Süleyman's Grand Vizier with extravagant tile decor.

▲ Taksim Square Gateway to the pedestrianized İstiklal Street, and heart of Istanbul's New District.

▲ Pera Museum Compact New District collection of world-class Orientalist paintings, Anatolian weights and measures, and Kütahya tiles.

▲ Galata Dervish Monastery Meeting place for dervishes, who whirl here once a week.

▲ Dolmabahçe Palace Opulent 19th-century European-style home of the sultans, accessible only by guided tour.

We were at the palace for the entire day. So if you do that, you may not see much else. If it were me, I'd concentrate on the mosques, I'd get in the Hagia Sophia line before opening (just the mosque not the virtual reality thing), then do the Blue Mosque followed by Mosque of Süleyman. If possible, see the area around the Blue Mosque and the Hagia Sophia at night.

Its really hard to make specific recommendation without knowing anything about you.

CL gave you Rick Steves’ extensive list, above. Just to clarify, Rick’s sight rating system uses 3-triangle ratings, as opposed to 5-star or 10-out-of-10 or other common systems.

Here’s how his triangle scores work:

▲▲▲ = Must See
▲▲ = Try hard to see
▲ = Worthwhile

I’d take a cruise on the Bosporus and a quick visit to the asian side. If you have time a walk up to see the outside of the Hagia Sophia and Blue Mosque although there are better views of it from nearby

The views are incredible from the water especially at sunset

Are you by any chance flying Turkish Airlines? They have a free extensive tour program for longer layovers.

Ignore the extensive list above, as it will only confuse you. That's for someone who has a week or more to spend.

I'd go with the Hagia Sofia and the Blue Mosque. The Spice Market is a fun stop and you can buy some wonderful spices as a souvenir of your 24 hour trip, or also head to the Grand Bazaar. I would probably stick with those three, and maybe just walk around Sultanahmet and some of the nearby areas, or down to the Bosphorus.

Where are you staying for the night?

Topkapi Palace is well worth seeing but it's quite large and generally takes a bit of time to go through. Chora Church is also lovely but pretty far out and would take some time to get to, so I would hold off on that.

Hagia Sophia and Topkapi were my two top sights there.

We spent two days in Istanbul last year. The highlights were Hagia Sofia, the Blue Mosque, Grand Bazaar, and the Basilica Cistern. We also did a cruise on the Bosphorus. Beautiful country with an interesting culture. Lots to see. Enjoy your trip!

There's on-going political instability in Istanbul right now; if you plan to be there soon then it might be good to monitor local media, plan to avoid disruption and demonstrations.