Shenzhen

Start at Shenzhen Museum near Civic Center, which tells how the city grew so fast after it became a Special Economic Zone. Entry is free and needs no booking; open Tuesday to Sunday, 10:00 to 18:00 (last entry 17:30), closed Mondays.

Walk OCT-LOFT in Nanshan, an old industrial estate turned into galleries, cafés and small shops. Take the metro to Qiaocheng East or Qiaocheng North and explore at your own pace.

Give a full day to the Dapeng Peninsula: Dapeng Fortress, a coastal fort built in 1394, with old walls, village lanes and the sea. Do not squeeze it between a museum morning and a border crossing.

See the modern districts of Nanshan and the centre: tech companies, big civic spaces and towers. Company campuses are to see from outside, not to tour.

From Hong Kong by high-speed train: from West Kowloon, the fastest trains take about 14 minutes to Futian (central Shenzhen) or 18 minutes to Shenzhen North. You clear Hong Kong and mainland immigration inside West Kowloon station before boarding.

From Hong Kong by MTR: take the East Rail Line to Lo Wu for Luohu (crossing open 6:30 am to midnight), or to the Lok Ma Chau Spur Line for Futian (6:30 am to 10:30 pm). You walk through both immigration checks. Easiest with light luggage.

From Guangzhou: the high-speed or intercity train usually takes under about an hour. Confirm on 12306.

Getting around: Shenzhen Metro gates take overseas contactless Visa, Mastercard, American Express and JCB cards, as well as UnionPay. You can also use the Shenzhen Tong QR code in Alipay.

Futian, Nanshan or Luohu. Choose by your route: where you arrive, where you spend evenings and how you leave. Luohu and Futian are handy for the Hong Kong land crossings.

Entry: Hong Kong and mainland China have separate immigration, so you clear both every time you cross. Sort out your mainland entry before you plan a day trip; crossing can take up much of the day.

Visa-free transit: China's 240-hour policy lets nationals of listed countries enter without a visa when travelling on to a third country, with an onward ticket. From Hong Kong by land it works only through West Kowloon station or the Hong Kong-Zhuhai-Macao Bridge, not Luohu, Futian, Huanggang or Shenzhen Bay.

Flying in instead: Bao'an Airport is one of the policy's entry ports.

At West Kowloon: the departure process usually takes 30 to 45 minutes and can start 90 minutes before the train. The real-name check stops 30 minutes before departure, so do not arrive late.

Phone and payment: sort out mobile data, and set up payment and identity checks (such as Alipay), before your first full day.

Hong Kong. Two neighbouring cities with different histories and daily rhythms. Start in one and end in the other.

Guangzhou. Older Cantonese Guangzhou with modern Shenzhen, usually under an hour apart by train. Five to eight days covers both.