I have found my turtle on the street in summer. Now there was another one asking questions about the same situation.
As example: I found an red eared slider alike turtle in northern or middle Europe in the summer.
How should the "rescue home" for an aquatic turtle look like?
(This home, which one could provide until the decision will be made what to do next.)
To give a turtle a short term home one needs:
If the outdoor temperature is above 20 degrees Celsius, the tub could stand outside; if not, it should get a place inside the house. It should be filled with water as high as one shell length of the turtle. The branch/stone will be placed inside, not too close to the tub walls (to prevent the turtle from falling out of the tub). If the tub is inside, the desk light will be placed to shine at the branch/stone as basking place. It should reach temperatures around 40 degrees Celsius.
For feeding one could use salad or dandelion leaves and gammarus from the pet shop. Gammarus should be given every day an amount that is eaten in few minutes and greens should be given how much the turtle likes. (One could not overfeed a turtle with greens. Depending of the kind of turtle it eats between 50% to 99% greens. For example mine need nearly 500g greens per day.)
Please keep in mind: this is for short term home only! For long term there are more questions here about feeding, basking, tank size and laying eggs.
The best option is to release it in an aquatic environment. Another alternative is to donate it to a local zoo, or even a pet shop - if they accept it.
If you choose not to, create an environment as similar as possible with a natural one.
I am not a specialist in turtles. You might actually need to provide a saltwater environment. Do your homework learning about that turtle before you do something harmful to it.
A veterinarian might be able to guide you.
