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5 Beds
4 Baths
3,085 sqft

$18,500,000

520 S Mashta, Key Biscayne FL, 33149

Price per sqft$5,996.76
Built in1961
Property size3,085 sqft
Property typeResidential
Courtesy of Maureen Jauregui with Coldwell Banker Realty

Overview

Active

Listed Aug 17, 2026

Updated 2 days ago

Seize a rare opportunity to create a landmark waterfront estate on one of the largest residential lots in Key Biscayne’s exclusive Mashta Island enclave. Spanning an extraordinary 22,140 square feet, this exceptional property offers 138 feet of pristine water frontage and sweeping open water views, providing an unparalleled setting for a world class residence. Plans by renowned architect, Pablo Corazzini of Vitalini Corazzini Architects, are available to the buyer, offering a thoughtfully conceived vision that takes full advantage of the property’s remarkable scale, premier waterfront setting, and spectacular sunsets. The proposed design creates an extraordinary canvas for sophisticated indoor-outdoor living and entertaining, should the buyer choose to pursue the concept. With its exceptional lot size, expansive water frontage, and coveted Mashta Island address, this is a truly irreplaceable opportunity to create a legacy estate in one of South Florida’s most prestigious waterfront communities.

$123,081/mo

Est. mortgage payment based on a $18,500,000 home price.

All estimates are provided by Luxury Presence for informational purposes only. Actual amounts may vary.

Additional information

MLS® ID
A12071221

Interior Features

Bedrooms
5
Bathrooms
4
Cooling
Yes
Heating
Yes
Basement
No

Exterior Features

Lot Size
0.51 Acres

Other Property Details

Taxes
$201,741
Tax Frequency
Annually
View
Yes
Pool
Yes
Waterfront
Yes
55+/Senior Community
No
MLS provider logo

Courtesy of Coldwell Banker Realty, Maureen Jauregui,
Listing Contact: 305-798-3124 

Based on information from Martin County REALTORS of the Treasure Coast, Inc. (RAMC) as of 10/29/2026. This information is for your personal, non-commercial use and may not be used for any purpose other than to identify prospective properties you may be interested in purchasing. Display of MLS data is usually deemed reliable but is NOT guaranteed accurate by the MLS. Buyers are responsible for verifying the accuracy of all information and should investigate the data themselves or retain appropriate professionals. Information from sources other than the Listing Agent may have been included in the MLS data. Unless otherwise specified in writing, Broker/Agent has not and will not verify any information obtained from other sources. The Broker/Agent providing the information contained herein may or may not have been the Listing and/or Selling Agent.

©2026 Martin County REALTORS of the Treasure Coast, Inc. All rights reserved.

Data last updated 4:44 AM UTC, 10/29/2026

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