No idea where to start!

[Freckletoes]

A lovely friend has offered to housesit, including kids, as a birthday present! So DH and I have a week to go somewhere without kids but I haven't a clue where to start! It probably needs to be Europe as only a week away. I don't do heat and sitting in the sun-pleasantly warm I can do but I really do wilt and fry in hot weather! We can do city or rural-a mix of both may be best. History, food, some active days. We not super active fill-every-minute types, but equally we can't do nothing for hours on end. Maybe somewhere a bit special as it's a significant birthday!
Suggestions and recommendations all gratefully received!

What's your budget like? Have you done much of Europe before?

my favourites if I had a bit ofmoney would be Copenhagen, Venice or Paris. Sardinia is beautiful butmight be too hot?. On a tighter budget I'd say Spain - Palma is a good city with easy acess to rural. Similar Barcelona. And you can embrace the siesta culture to avoid hottest time of day.

Lucky you!

Carcassonne, Florence, Avignon, Copenhagen, Barcelona, Malta/Gozo, Crete (before end of June). I wish I had your problems!

Re-reading your OP, I'd say Florence or Siena. And make sure you book a flat or villa (via VRBO or similar), with a terrace, rather than a hotel. Great city, great food, history galore, rural right next door.

When are you planning to go? Prague springs to mind. Lake Como?

Have to go the first week in August to fit friend's time off. Haven't really seen a lot of Europe-since honeymoon 15 yrs ago have only managed UK hols with kids, then had 6 yrs without any holidays until last year when we got away to Southern Spain to a friend's villa which was too hot and too dull for us! So most stuff was done pre marriage!
Some suggestions cropping up that I have very long listed

dont rule out transatlantic.. once took me 19 hours to get to boring euro destination, can get to miami in about 7. or newyork. plenty of people do it just for a couple of days. or argentina or rio. or hongkong. easy if you dont have jet lagged kids to look after.