Henry George proposes to "abolish all taxation save that upon land values." (This has been called the "Single Tax.") We already take some rent in taxation - directly, in the form of the real property tax. We only have to make some changes in our modes of taxation to take it all.
We must realize, however, that the present system of "property taxation" is a tax on real estate, and real estate is comprised of two very different elements. "Real estate" includes wealth (buildings and improvements) as well as land. So, the first step toward implementing Henry George's remedy would be to increase the "property tax" on land and simultaneously decrease the tax on improvements.
Suppose, instead, a levy of 6% on the land value alone — with no taxes on improvements. What would the property tax bill be for each of these parcels? Each parcel has the same land value — so the tax would be the same: $600, whather the land is put to use or not. So we see that — compared with the current system — a tax on land value penalizes land speculation and rewards development!
Simply removing the tax burden on buildings would be an immense boon to both urban and rural economies — but George's remedy would not stop there. Its ultimate goal would be to remove all taxation on the production of wealth, substituting the collection of the full rental value of land for public revenue. Ideally, the value of minerals, and all manner of natural resources and opportunities (such as broadcast frequencies, and geosynchronous orbits), would be collected for public revenue.
Some argue that the rent of land could only be collected once, because if the rent is collected, the price of land will be taken away! Fortunately, that contention is erroneous. The selling price of land depends on a private landholder being able to collect rent in the future. If all of the land rent is collected by the community, the selling price will disappear — but, the rental value will remain as long as there is demand for the site. Here's more on the relationship between land rent and selling price.