I'm using maps in my app and want to place other objects on top of the map. My understanding of the painter model that corona uses is that objects created later are placed on top of objects created earlier.

Any ideas what I'm doing wrong?

Use groups. Groups are drawn in their order of creation. Assign objects to the groups. When a group is drawn, the objects inside a group are drawn in order of their index.

That doesn't work - see my reworked mapview code below. You can test this in xcode simulator

--
-- Abstract: MapView sample project
-- Demonstrates the API for embedded maps and location data (currently iOS-only)
--
-- Version: 1.0
--
-- Sample code is MIT licensed, see http://developer.anscamobile.com/code/license
-- Copyright (C) 2010 ANSCA Inc. All Rights Reserved.

display.setStatusBar( display.HiddenStatusBar )

-- Load external Lua libraries (from project directory)
local ui = require( "ui" )

local locationNumber = 1 -- a counter to display on location labels
local currentLocation, currentLatitude, currentLongitude

local background = display.newImage( "bkg_grass.png", true )
background.x = display.contentWidth / 2
background.y = display.contentHeight / 2

local label = display.newText( "Maps not supported in Corona Simulator.", 20, 70, native.systemFont, 14 )
label:setTextColor( 255, 255, 255 )

local label2 = display.newText( "(Build for XCode Simulator or iOS device.)", 20, 95, native.systemFont, 14 )
label2:setTextColor( 255, 255, 255 )

-- Create a native MapView (requires XCode Simulator build or device build)
-- You can create multiple maps, if you like...
myMap = native.newMapView( 20, 20, 300, 220 )
myMap.mapType = "normal" -- other mapType options are "satellite" or "hybrid"

-- The MapView is just another Corona display object, and can be moved or rotated, etc.
myMap.x = display.contentWidth / 2
myMap.y = 120

-- Initialize map to a real location, since default location (0,0) is not very interesting
myMap:setCenter( 37.331692, -122.030456 )

mymapgroup = display.newGroup()
mymapgroup:insert( myMap )

shadow = display.newRect( 7, 7, 306, 326 )
shadow:setFillColor( 0, 0, 0, 120 )

-- A handler for the native keyboard
local fieldHandler = function( event )
-- Hide keyboard when the user clicks "Return" in this field
if ( "submitted" == event.phase ) then
native.setKeyboardFocus( nil )
end
end

-- A native text input field (requires XCode Simulator build or device build)
inputField = native.newTextField( 10, 252, 300, 28, fieldHandler )
inputField.font = native.newFont( native.systemFont, 16 )
inputField.text = "Broadway and Columbus, San Francisco" -- example of searchable location
inputField:setTextColor( 45, 45, 45 )

-- A function to handle the "mapAddress" event (also known as "reverse geocoding")
local mapAddressHandler = function( event )
locationText =
"Latitude: " .. currentLatitude ..
", Longitude: " .. currentLongitude ..
", Address: " .. event.streetDetail .. " " .. event.street ..
", " .. event.city ..
", " .. event.region ..
", " .. event.country ..
", " .. event.postalCode

local alert = native.showAlert( "You Are Here", locationText, { "OK" } )
end

-- Create buttons and their functions:

local button1Release = function( event )
-- This calls a Google web API to find the location of the submitted string
-- Valid strings include addresses, intersections, and landmarks like "Golden Gate Bridge", "Eiffel Tower" or "Buckingham Palace"
latitude, longitude = myMap:getAddressLocation( inputField.text )

-- Move map so this location is at the center
-- (The final parameter toggles map animation, which may not be visible if moving a large distance)
myMap:setCenter( latitude, longitude, true )

markerTitle = "Location " .. locationNumber
locationNumber = locationNumber + 1

-- Add a pin to the map at the new location
myMap:addMarker( latitude, longitude, { title=markerTitle, subtitle=inputField.text } )
end

local button2Release = function( event )
-- Fetch the user's current location
-- Note: in XCode Simulator, the current location defaults to Apple headquarters in Cupertino, CA
currentLocation = myMap:getUserLocation()
currentLatitude = currentLocation.latitude
currentLongitude = currentLocation.longitude

-- Move map so that current location is at the center
myMap:setCenter( currentLatitude, currentLongitude, true )

-- Look up nearest address to this location (this is returned as a "mapAddress" event, handled above)
myMap:nearestAddress( currentLatitude, currentLongitude )
end

local button3Release = function( event )
myMap:removeAllMarkers()
locationNumber = 1 -- reset counter for popup labels
end

local button1 = ui.newButton{
default = "buttonGreen.png",
over = "buttonGreenOver.png",
onRelease = button1Release,
text = "Find Location",
emboss = true
}

local button2 = ui.newButton{
default = "buttonOrange.png",
over = "buttonOrangeOver.png",
onRelease = button2Release,
text = "Current Location",
emboss = true
}

local button3 = ui.newButton{
default = "buttonRed.png",
over = "buttonRedOver.png",
onRelease = button3Release,
text = "Remove All Markers",
emboss = true
}

button1.x = display.contentWidth / 2; button1.y = 320
button2.x = display.contentWidth / 2; button2.y = 380
button3.x = display.contentWidth / 2; button3.y = 440

-- A listener for the address lookup result
-- (This could also be a table listener on the map itself, in case you have more than one simultaneous map.)
Runtime:addEventListener( "mapAddress", mapAddressHandler )

http://developer.anscamobile.com/reference/index/objecttofront

as far as i know maps are a native object and thus rendered above the corona display, like web views

This definitely doesn't look like a happening thing.

My rect is below any native ui element, not matter what I do - including calling object:tofront()

ANSCA - please advise, this basically means the end of my project.

Ahh, ok. Didn't saw the mentioning of a native display object. They also draw ontop of over display objects.

Hey @3saul: any update on this problem. did you find a solution or an alternative?
Thanks
CV