Parcels: Cuyahoga County Parcels can be displayed by selecting either one of the following:

All Parcels (Fiscal Tax Map): Parcels with real property appraisal characteristics.
Vacant Parcels (Fiscal Tax Map): A subset of Tax Parcels including only vacant taxable land uses (TAX_LUC ends with '000'), City Land Bank (EXT_LUC=6411), or County Land Bank (EXT_LUC=6210). "Vacant" parcels are those without structures, according to the County Fiscal Office.

Superfund & RCRA Sites (EPA)

Active RCRA: An Active RCRA site simply means that the property owner has registered with EPA as either a Generator, or a facility which Treats, Transports, Stores or Disposes (TSD) hazardous waste under the Resource Conservation and Recovery Act program. These hazardous waste handlers may include facilities as large as industrial manufacturing sites or as small as dry cleaners and auto mechanic shops. Registration as a RCRA permitted site is an administrative requirement and does not imply contamination. EPA's Facility Reporting System documentation (PDF) provides details on RCRA and other EPA programs (page 9 covers RCRA categories).
Superfund Sites: Superfund Sites are properties which have reported to EPA under the Superfund Enterprise Management System (SEMS) and SEMS National Priorities List (NPL). Superfund is a program administered by the EPA to locate, investigate, and clean up the worst hazardous substance contaminated sites throughout the United States under the Federal Comprehensive Emergency Response, Compensation and Liability Act (CERCLA). Such reporting may include known releases or threatened releases of hazardous substances, pollutants or contaminants.
Superfund Site Boundaries: This layer contains polygons depicting U.S. EPA Superfund Site boundaries, defined as "the sum of all of the Operable Units (OU) and the current understanding of the full extent of contamination. For Federal Facility sites, the total site polygon may be the Facility boundary. As site investigation and remediation progresses, OUs may be added, modified or refined, and the total site polygon should be updated accordingly. Superfund features are managed by regional teams of geospatial professionals and remedial program managers (RPMs), and Shared Enterprise Geodata Services (SEGS) to harvest regional data on a weekly basis to refresh the national dataset and feature services. The data and corresponding metadata records can be downloaded from the EPA Environmental Dataset Gateway (EDG)."

Landfills: The first three layers in this group are from the Ohio EPA Division of Materials & Waste Management:

Active Solid Waste Facilities: Point representations of solid waste facilities that are currently in operation. Symbols depict the type of facility.
Historic Solid Waste Sites: Point representations of closed solid waste sites. Refer to the attribute data for more details, such as Waste Type and Year Closed.
Cuyahoga County Dump Soils (c.1980): This layer shows soils that are designated as ‘Du’ or Dump Soils through the National Cooperative Soil Survey of the US Department of Agriculture. The “Soil Survey of Cuyahoga County” report was issued in 1980. According to the Survey, Dump Soils are: “miscellaneous areas consisting mostly of cement, bricks, cinders, home refuse, and other debris of industrial origin. Some areas are sanitary landfills containing mostly home refuse. Most areas are 20 to 200 acres in size. The depth of the fill material ranges from about 10 to 100 feet." A digital copy of the Soil Survey of Cuyahoga County is currently available on Google Books.

Conservation & Protected Land: Several layers show the locations of conservation easements and other protected lands:

Priority Conservation Area: Priority Conservation Area (PCA) is an area recognized as a significant space to be preserved as open space. In Ohio, PCAs are identified in a watershed-specific Balanced Growth Plan that has been approved by local communities and endorsed by the Ohio EPA. This is a voluntary designation and is specifically geared toward watershed protection under the Ohio Balanced Growth Program. Four approved Balanced Growth plans have been completed in portions of Cuyahoga County: Big Creek Watershed, Chagrin River Watershed, Chippewa Creek Watershed, and Furnace Run Watershed. A PCA designates an area for protection and restoration that may be critically important for ecological, recreational, heritage, agricultural, and public access areas. PCAs can also be significant for their contribution to water quality and general quality of life.
Conservation Easements (WRLC): Western Reserve Land Conservancy (WRLC) is the largest land trust in Ohio and one of the largest land trust organizations in the nation. This dataset include all protected properties owned or maintained by WRLC, and covers much of Cuyahoga County. The dataset is maintained directly by WRLC, and represents the most up to date inventory in Cuyahoga County.
Conservation Easements (NCED-All Other): The National Conservation Easement Database (NCED) is a nationwide compilation of conservation easements. The NCED relies on the voluntary submittal of conservation easement data by participating organizations and is not necessarily an exhaustive list. The WRLC land holdings are excluded from this layer.
ODNR Protected Lands: Today, 141 State Nature Preserves and natural areas have been dedicated in Ohio. Although the majority of preserves are owned and managed by the State, some preserves are leased to local park districts for management . Other preserves are owned by non-governmental agencies. Some private landowners have dedicated their lands as preserves, and those lands are protected by the State. Access to some preserves is available by a no-fee permit from ODNR.