Something To Declare: Porto; Mauritius; risk management; cruise tips up by £25

Destination of the week: Porto

High summer is ideal timing for short breaksto some of Europe's lesser-known cities,such as this gem on the Douro river in northern Portugal. The port industry is one attraction but there is much else, from antique trams and elegant architecture to a beach resort on the edge of town. It is also perhaps the cheapest big city in the eurozone.

Bargain of the week: Mauritius

The Indian Ocean island described by Alexander Armstrong is the location for some impressive deals this summer. Mercury Direct (0800 781 4893; mercurydirect.com) is offering a week's all-inclusive at the "three-star-plus" Casuarina Resort for £1,291, departing 1 August. The price includes Air France flights from Heathrow via Paris; the outbound trip involves an all-day wait in the French capital, but you are allowed to leave the airport.

Best at Travel (020-7849 4100; bestattravel.co.uk) is packaging the deluxe One&Only resort with non-stop Air Mauritius flights from Heathrow: a week departing 14 August, half board, in a Junior Suite, costs £2,138 per person based on two sharing.

Warning of the week: Risk management

Professor David Spiegelhalter is the Winton Professor of the Public Understanding of Risk at Cambridge University. Last week, he talked about the relative risks of different forms of transport. This week, we invited him back to ask: what advice would he most want to give to holidaymakers who are flying off on holiday this weekend from Gatwick or Manchester airport?

"I'd warn against roaring around on rented motorbikes and mopeds with no helmet on dirt roads. Especially after a few drinks, it's really idiotic. (I have rented a moped myself, but only when sober.)

"I'd also be careful about some down-market whitewater rafting operations.

"The most crucial thing is not to get plastered and make an idiot of yourself. Getting drunk and trying to do something athletic is completely ridiculous – particularly diving into a swimming pool that's only a few feet deep."

Tip of the week: Cruise tips up by £25

Royal Caribbean has increased the guideline amounts for tipping on its cruises. Starting this month, the daily recommended rate for a cabin attendant rises from $7 to $10 per couple, while tips for dining-room staff increase from $12.50 to $13.30. For a two-week cruise this represents a total of £217 per couple – an increase of £25 from the previous level of £182.

"This is Royal Caribbean's first tip adjustment in 13 years," says the company. "It puts our suggestions in line with our competitors."

The purpose of the gratuities, says the cruise line, is "to help guests express their gratitude for the outstanding service they experience".