In combined networks, topology shows an integrated Cisco Meraki network that has MX Security Appliances, MS Switches, and MR Access points. Squares represent MX security appliances, rectangles represent MS switches, stacked rectangles represent MS physical switch stacks, and circles represent MR access points. Non-Meraki equipment is also detected if it is one hop away (and will appear as an empty diamond); depending on the protocols supported by a non-Meraki device, the topology view may be able to discern LLDP data like model type, IP, and manufacturer. Meraki devices in a different network will be denoted by blue diamonds.
Source:
https://documentation.meraki.com/MS/Monitoring_and_Reporting/Network_Topology