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Just to add to what Mark wrote, normally CDP and LLDP will only show neighbors connected by L2. So even if its enabled, assuming you don't have access to transit device, you might only be able to "see" the next device beyond yours.
For traceroute, there are configurations that will "hide" devices, for example, a GRE tunnel won't show physical hops between the GRE end-points.
In other words, it can sometime be very difficult to determine a network's physical topology.
