What portion of the sale of a property outside the US will you need to pay taxes on? Will you be paying taxes on the total sale price or only on the gain?
In this particular case you will need to report the net income(gain/loss) from the sale of the property.
The same question is discussed in on Bankrate and refers to Schedules D and E, and IRS form 4797 to fill out depending on the type of property sold and it's past use but I'd check with an accountant as these types of sales may get complicated from the tax purpose.
You generally pay taxes on gains, i.e.: you take your sale proceeds, deduct your cost basis (which may or may not be the amount you paid for the property), and calculate your tax liability on the difference. In the case of international transaction, such as selling property in a different country, you should always consult with a tax accountant (EA/CPA licensed in your state) that will help you identify relevant treaty clauses (if there's a treaty between the US and that country on tax issues), and additional potential deductions (for example, taxes you already paid/accrued on the same gains in that foreign country).
Depending on the use, and how you got to own the property, additional reporting may be required. Keep in mind the FBAR and FATCA requirements, and various additional forms that must be attached to your tax return since you have significant amounts of money abroad. Don't take these requirements lightly, while not affecting your tax liability in any way - just not attaching one of these pieces of paper may cost you $10000 and more in penalties.