What is it?

Tehran is a metropolis of some nine million people (fifteen million in the greater urban area) that climbs the southern slopes of the Alborz Mountains, so that on a clear winter day you can stand in a downtown traffic jam and look up at snow-covered peaks. It is a city of dazzling contrasts: the mirrored halls and painted tilework of the 19th-century Golestan Palace sit a short walk from the labyrinthine Grand Bazaar, where the scent of saffron, dried limes and grilling kebab mingles with the clang of copper workshops and the shouted prices of carpet dealers. Underground in the vaults of the Central Bank, the National Jewelry Treasury holds the largest uncut pink diamond in the world and a globe made of 51,000 gemstones — one of the most extraordinary and least-visited collections on earth. Uptown in Tajrish and Darband, Tehranis escape the traffic on foot, sipping tea and smoking qalyan on platforms suspended over a mountain stream, while in the galleries of Vali Asr and the cafés of Enghelab a young, highly educated population debates film, poetry and politics. Add the modernist icon of Azadi Tower, the sweeping Tabiat Bridge and the astonishing carpets and Persian miniatures of the city's museums, and Tehran reveals itself not as a stopover but as the beating, complicated heart of modern Iran.

Where is it?

Tehran lies in north-central Iran, spread across a plateau at 1,200–1,800m altitude at the foot of the Alborz range, with Mount Damavand visible to the northeast on clear days. Key sights cluster in the historic south (Golestan Palace, Grand Bazaar, National Museum), the central spine along Vali Asr Street, and the affluent north (Niavaran and Sa'dabad palace complexes, Tajrish Bazaar, Darband trailhead). Come in April–May or late September–early November for mild air and clearer skies; summers are hot and smoggy, and winters are cold but bring skiing at Dizin and Shemshak, less than two hours away.

What makes it worth it?

Almost every visitor arrives with an image of Iran shaped by headlines and leaves talking about something entirely different: the relentless, disarming hospitality. Strangers invite you for tea, taxi drivers refuse your fare, families share picnic food in Laleh Park, and shopkeepers press pistachios into your hands with a smile — "I came for the history and stayed for the people" is the single most repeated sentiment from travellers here. Tehran also gives you the emotional register of the whole country in one place: grief and beauty in a Persian poem read aloud, pride in a 5,000-year-old civilisation on display at the National Museum, and the quiet defiance of a generation carving out space for art and music. Years later you may forget which palace had which mirror hall, but you will remember the taste of a fresh-grilled kebab with charred tomato and sumac, the sound of the call to prayer echoing over eight lanes of traffic, and the family who took you home for dinner after five minutes of conversation. Few capitals so thoroughly dismantle a traveller's preconceptions.

How accessible is it?

Physically it's easy — this is city sightseeing on flat streets with an excellent, cheap metro (roughly $0.10–0.30 a ride) and abundant taxis, though the traffic and air quality can be tiring and pavements are uneven. Logistically it's the paperwork that requires planning: most nationalities need a visa, obtainable as an e-visa or on arrival at Imam Khomeini International Airport for many passports, while US, UK and Canadian citizens must travel on a guided tour with an approved itinerary. International bank cards do not work in Iran, so you must bring cash (euros or dollars) and exchange it locally or load a prepaid tourist debit card; travel insurance covering Iran should be bought separately. Costs are low by global standards — hostel beds from $10, decent hotels $30–80, a full kebab meal $5–12, museum entry $2–8 — so $40–70 a day is comfortable for independent travellers. Women must wear a headscarf and modest clothing in public; check current government travel advisories and regional conditions before booking, and allow three to four days to do the city justice.