Here are some popular GIS (Geographic Information System) and mapping URLs that are commonly visited by users interested in spatial data and mapping:

1. ArcGIS Online - https://www.arcgis.com
2. Google Maps - https://www.google.com/maps
3. OpenStreetMap - https://www.openstreetmap.org
4. Mapbox - https://www.mapbox.com
5. Esri - https://www.esri.com
6. QGIS - https://www.qgis.org
7. Carto - https://www.carto.com
8. Bing Maps - https://www.bing.com/maps
9. GeoServer - http://geoserver.org
10. MapQuest - https://www.mapquest.com

These websites provide a range of GIS and mapping services, including interactive maps, geospatial analysis, data visualization, and more. Whether you are a GIS professional, a researcher, or simply interested in exploring maps, these URLs offer valuable resources for working with spatial data and discovering geographic information.